Save and Export ask before replacing a file that an added extension names

After the desktop save panel closes, the app adds the file type's
extension to a name typed without it (or with one the save does not
write). The panel asked only about the name as typed, so on Linux
typing `card` with `card.vectorcraft` in the folder wrote over
`card.vectorcraft` without a question. On Linux the save panel is the
XDG desktop portal, and its GTK and GNOME file choosers return the
name as typed. Windows and macOS add the extension themselves only
when the panel lists file types, and the panels of Document Info's
Save, the presets dialogs' Export…, the CSS Properties export, the
swatch and graphic style library saves and the Libraries panel's
export list none.

When the added extension names a file that exists, Save, Save As, Save
a Copy, Save as Template, the exports and the other writes through a
save panel now ask "“card.vectorcraft” already exists. Replace it?"
first (dialog `replaceFile`). OK runs the write again with the same
answer and replaces the file. Cancel writes nothing and shows the
dialog it was asked over again. The host reports whether a file exists
through a new `Services::exists`.

Docs: docs/control-protocol.md, docs/target-app-parity.md.

docs/control-protocol.md

@@ -109,7 +109,7 @@ the two can still win that race.
 | `app.export` with `useArtboards` | `{path, useArtboards: true, range? \| artboards?, …}` | Export As: PNG, JPEG and WebP write one file per chosen artboard (default all; SVG does so for a `range`), `<path stem>-<artboard>.<ext>`, and return `{path, files: [path…]}`; a PDF keeps them as pages of `path`. `useArtboards: false` covers the bounds of the visible art. The menu's Export As… is `file.exportAs`: the `exportAs` dialog (`format`, `useArtboards`, `all`, `range`), then a save dialog and the format's options: `pngOptions` / `jpgOptions` / `webpOptions`, `svgOptions`, or `savePdf` for a PDF with Use Artboards |
 | `ui.dialog.*` on `gradientStop` | `{field: "color" \| "opacity" \| "location", value}` | double-clicking a stop on the Gradient tool's annotator opens its popover (fields `index`, `x`, `y`, `tab`); set `color` (hex), `opacity` or `location` (percentages) and `ui.dialog.confirm` to apply them to the selected stop. `gradient.selectStop {index}` picks the stop the annotator, the panels and Delete/←/→ (`ui.key`) act on |
 | `engine.execute` `ui.savePdfDialog` | `{path?, preset?, range?, …document.exportPdf options}` | opens the Save PDF dialog (`file.export.pdf` with no params opens it too). Its fields are the `document.exportPdf` options: set `compatibility` with `ui.dialog.set {field: "compatibility", value: "1.5"}`, a whole section with `{field: "compression", value: {…}}`, the artboards with `__allArtboards: false` and `range`, the visible section with `__section` (General, Compression, Marks and Bleeds, Output, Advanced, Security, Summary). `ui.dialog.confirm` writes `path` (else asks for one), returns `{path, bytes, warnings}` and opens the file when `viewAfterSaving` is set |
-| `file.save` / `file.saveAs` / `file.saveCopy` / `file.saveAsTemplate` (via `engine.execute`) | `{path?, format?, options?, svg?}` | Save writes the document's own file in its own format (a document opened from or saved as SVG/PDF saves as that again; the result's `warnings` say what the format loses). With `path` the file is written at once (Save As or a Copy to an SVG path without SVG options first opens SVG Options, below). Without one (never saved, a converted older file, Save As, a Copy, a Template) the app shows a save panel with one file type per save format (`vectorcraft`, `template`, `pdf`, `svg`, `svgz`), then the format's options: SVG opens the `svgOptions` dialog (below; returns `{"pending": "svgOptions", "path"}`), PDF the `savePdf` dialog (its `__save` field names the save command); `ui.dialog.confirm` finishes the save. On the web a `saveOptions` dialog (fields `path`, `format`) first names the file and picks the format. `file.formatOptions {format?}` reads the options a save would use. `file.revert` opens a `confirm` dialog (`{"pending": "confirm"}`); `ui.dialog.confirm` reloads the saved file in the same tab |
+| `file.save` / `file.saveAs` / `file.saveCopy` / `file.saveAsTemplate` (via `engine.execute`) | `{path?, format?, options?, svg?}` | Save writes the document's own file in its own format (a document opened from or saved as SVG/PDF saves as that again; the result's `warnings` say what the format loses). With `path` the file is written at once (Save As or a Copy to an SVG path without SVG options first opens SVG Options, below). Without one (never saved, a converted older file, Save As, a Copy, a Template) the app shows a save panel with one file type per save format (`vectorcraft`, `template`, `pdf`, `svg`, `svgz`), then the format's options: SVG opens the `svgOptions` dialog (below; returns `{"pending": "svgOptions", "path"}`), PDF the `savePdf` dialog (its `__save` field names the save command); `ui.dialog.confirm` finishes the save. A name typed in the panel without the file type's extension gets it; when a file of that name exists, which the panel did not ask about, the save (and every export or other write through a save panel) answers `cancelled` and opens a `replaceFile` dialog (fields `message`, `detail`, `path`): `ui.dialog.confirm` writes that file, `ui.dialog.cancel` writes nothing. On the web a `saveOptions` dialog (fields `path`, `format`) first names the file and picks the format. `file.formatOptions {format?}` reads the options a save would use. `file.revert` opens a `confirm` dialog (`{"pending": "confirm"}`); `ui.dialog.confirm` reloads the saved file in the same tab |
 | SVG Options (`engine.execute` of `file.export.svg`, `file.saveAs`, `file.saveCopy`) | `{}` / `{path?, svg?: {…}}` | `file.export.svg` without params, and Save As or Save a Copy to an `.svg`/`.svgz` path without SVG options, open the `svgOptions` dialog (`ui.dialog.set` its fields: `styling`, `outlineText`, `images`, `objectIds`, `decimals`, `minify`, `responsive`, `fewerTspans`, `metadata`, `preserveEditing`, `useArtboards`, `allArtboards`, `range`, `showCode`, `profile` (`svg11`/`tiny12`), `encoding` (`utf8`/`utf16`/`latin1`), `embedFonts`; `ui.dialog.confirm` exports or saves and remembers the choices). With `svg: {…}` (the `document.formats` SVG options) they run directly. `app.save {path?, svg?}` takes the same options; a document saved as SVG saves as SVG again with the same options |
 | `engine.execute` `file.place` | `{paths?}` / `{path \| name+dataBase64, …file.place params}` | with no file, picks files and opens the `place` dialog; with `paths`, opens it for them (fields `files`, `link`, `template`, `replace`; `__replace` says whether Replace applies, `__info` describes each file). `ui.dialog.confirm` places one file centred in the view (or in place of the selected object) and loads the place cursor with several (`file.place.queue`). With a file, it runs `file.place` centred in the view. Files dropped on the window with no document open open. On the web, files dropped on the canvas are placed at the drop point (linked; Shift embeds) and files dropped off it (the tab bar) open, as in Illustrator; desktop drops carry no pointer position, so documents (native, SVG, PDF, `.ai`, EPS, DXF, EMF/WMF) open as tabs of their own and pictures and text are placed in the middle of the view. Swatch libraries and color books (`.vcswatches`, `.gpl`, `.ase`, `.acb`), graphic style libraries (`.vcstyles`), Libraries panel files (`.vclibrary`), presets (`.vcflattener`, `.vcpdfpresets`, `.vcprintpresets`, `.vcperspective`), plug-ins (`.wasm`) and shortcut sets (`.kys`, in Import Shortcut Set) open wherever they are dropped, as File › Open opens them. With the cursor loaded (`ui.inspect` → `tool: "place"`, `toolOptions: {count, current, name, names}`), `ui.pointer` clicks and drags place files and `ui.key` ←/→/↑/↓ and Escape cycle and discard them |
 | `app.export` raster options | `{path?, format: png \| jpg \| webp, ppi?, background?, antiAlias?, interlaced?, quality?}` | `ppi` sets the pixel size (72 = one pixel per point) and is stored in the file; `background` is `transparent`, `white`, `black` or `"#rrggbb"`; `antiAlias` is `none`, `art` or `type` (text snapped to pixels); `interlaced` writes an Adam7 PNG. The PNG Options dialog (`pngOptions`; `jpgOptions` / `webpOptions` for the other raster formats) has the same fields: fill them with `ui.dialog.set` and press OK with `ui.dialog.confirm` |

docs/target-app-parity.md

@@ -623,6 +623,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - PDF export and print composition use the optional shared guarded writer ([pdf-backend.md](pdf-backend.md)); app drawing and output policy and desktop printer submission remain in their existing layers. The shared reader keeps the app-owned import adapter; synthetic tests cover layer and overprint state across windows, long operands, inline images, failed decoding, document limits and incomplete tails. Empty and populated metadata key presence is regression-tested, and CI checks the immutable backend source.
     A PDF, or a `.ai` read through its PDF part, whose spot inks have the same values but different names opens with a spot swatch for each ink. The solid fills and strokes of paths and type, and the stops of gradients on paths, link to the swatch of the ink they are painted in, the points of a gradient mesh in one of these inks keep the ink's color, and PDF export writes each of these inks as its own separation (`pdf/src/tests_import_color.rs`). Paint in these inks inside pattern cells, soft masks and type 3 glyphs, and gradients on type in these inks, still import as RGB. Type in one of these inks can also import as RGB when type in another Separation or DeviceN ink is shown with no path drawn between them.
   - `.vectorcraft` (lossless JSON, compressed, atomic saves, save down to v1), Save As with a format chooser, Save a Copy, Revert, templates, Data Recovery after a crash (browser tabs hold their copies with Web Locks too, so a background tab's copies are never taken for a crash's, and a tab repairs copies another removed when it resumes: #367), background save and export. The desktop app writes its warnings and errors (graphics adapter, a lost graphics device, panics the guard recovered from) to standard error and to `logs/vectorcraft.log` next to the preferences, the two previous runs kept and each file capped at 16 MiB, so a launch without a terminal still leaves something to attach to a bug report (#465). Native documents with a lot of path data (traced or generated art, in layers, symbols or patterns) are saved as compact JSON, about a fifth of the size; small documents stay pretty-printed (#1492). Saving to a network drive on macOS falls back to a plain fsync when the share refuses a full flush (#1625, part of #1620; not confirmed on a real share), and a save still succeeds when a folder refuses the temporary file, the rename over the document or copying permissions: the content is written elsewhere first and copied in, and a failed copy keeps the temporary file and names it (#1649, part of #1620). A document opened by a relative path finds its relatively linked images, and `vectorcraft-cli convert` lists what reading the input left out as `importWarnings` (#1606, fixes #1604).
+    A name typed in the desktop save panel without the file type's extension gets it, and when a file of that name exists, which the panel did not ask about, Save, Save As, Save a Copy, Save as Template, the exports and every other write through a save panel ask before replacing it (dialog `replaceFile`; Cancel writes nothing).
   - macOS: the save sheet of Save As, Save a Copy, Save as Template and the first Save of a new document has a Format menu that lists each format the save can write, with the suggested file's format selected. Choosing a format changes the extension in the name field, and a name typed without an extension gets the chosen format's. A name typed with another listed extension is saved in that format. The menu is set up before the sheet opens; a save panel with one file type is shown by rfd as before (#866, `apps/vectorcraft/src/mac_save_format.rs`).
   - Save as Template writes a PDF-compatible `.ait` as well as a `.vctemplate`, which stays the default: the save panel and the web build's Save as Template dialog list both, and New from Template opens the `.ait` as an untitled document with its layers and art (`file.saveAsTemplate {format: "ait"}`, or a path ending in `.ait`).
     Save as Template always writes a file named with its template type's extension: `file.saveAsTemplate` saves a path ending in another format's extension (`card.png`) as `card.vctemplate` (or `card.ait`), the desktop save panel adds `.vctemplate` to a name typed with a Save As format's extension (`card.pdf.vctemplate`), and `file.saveAs` and `document.save` refuse `ait` with an error that names `file.saveAsTemplate`.