Clipboard: Copy and Cut make the system clipboard's formats on the background thread

Copy and Cut made the system clipboard's formats in the frame that ran
them. The formats include the SVG markup and a PNG of the selection at
1 px per pt, up to 4,096 px a side. In a release build on Windows, Copy
of 50,002 rectangles on a 1600 x 1200 pt page took 1.00 s in its frame.

The thread that writes background saves and exports now makes the
formats from a copy of the clipboard, and the app writes them in a
later frame. The same Copy takes 0.18 s in its frame, and the SVG and
PNG are the same bytes. While that thread has a save, an export, a print or
a recovery copy to finish, Copy and Cut make and write the formats at
once. A later Copy or Cut, or text copied in a field or with the Type
tool, drops formats that are not written yet. Until they are written,
Paste on the canvas takes the internal clipboard, and while a text
field or the Type tool has the keyboard the app waits for them.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -2312,8 +2312,12 @@ as `document.open` reads one), `clipboard.importImage {dataBase64, mime?}` (an e
 physical size) or `clipboard.importText {text}` (point text in the default type style), each centred on `center`
 (default: the first artboard); then any `edit.paste*` command pastes it. The desktop app does this itself: Copy and
 Cut publish the formats to the system clipboard, and a Paste outside text editing first reads what another app
-copied (SVG, then PDF, then text, then a bitmap; SVG markup in text counts as SVG). Pasting what VectorCraft copied
-keeps the lossless internal clipboard. Windows carries every format both ways and pastes a bitmap from PNG, else
+copied (SVG, then PDF, then text, then a bitmap; SVG markup in text counts as SVG). A background thread makes the
+formats and they are published when they are ready. While that thread has a save, an export, a print or a recovery
+copy to finish, Copy and Cut make and publish them at once. When another Copy or Cut, or a copy of text in
+VectorCraft, comes first, they are dropped. Pasting what VectorCraft copied keeps the lossless internal clipboard,
+also before its formats are published. While a text field or the Type tool has the keyboard, the app waits for
+them. Windows carries every format both ways and pastes a bitmap from PNG, else
 from the device-independent bitmap screenshots copy (`CF_DIBV5`, then `CF_DIB`; alpha kept, opaque when it is zero
 throughout, at most 32768 px a side); macOS and Linux carry one format (the text, else the PNG) and paste text and
 bitmaps (macOS the pasteboard's PNG, else TIFF, as screenshots copy them). On the web Copy publishes SVG text, and

docs/target-app-parity.md

@@ -568,6 +568,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - Placed documents: File › Place of a `.vectorcraft` file links to it by default (`file.place`'s `link`): one locked object showing an artboard of the document (or its art's bounds), read the way placing it without Link reads it, its symbols, patterns and images kept apart from the document's; without Link (or from bytes, not a file) it is an editable copy as before. It stays vectors in every output (SVG, PDF, EPS, EMF, DXF), and so do placed documents inside it, read from their own files up to 8 levels deep (documents that place each other stop there). On screen they draw from bitmaps cached per file and zoom step, shared by every copy and made in the background (a placeholder until ready), so a sheet of them redraws in about a millisecond; exports and prints draw them exactly. Like linked images, a save keeps only a preview of each (JPEG when opaque) unless Include Linked Files; output, and zooming past the preview, read the file again, falling back to the preview with a warning when it is gone or changed. Saves for older versions write them as plain art. Links check, update, relink, Update Links on open, Link Info (the artboard's size), Placement Options, Break Link (also Embed, Object › Expand: the editable copy placing without Link gives, its resources joining the document), Edit Original (the document in a new tab) and the Links panel cover them; saving a document updates the open documents that place it. The native format (v4) keeps data of 8 KB or more after the JSON instead of base64 in it.
   - Desktop print transport uses `craft-print` for CUPS and modern Windows. Sheet composition, copies, separations and colour management remain in VectorCraft; Windows 7 retains WMI and the installed PDF viewer. The print-preview and physical-device fidelity gaps remain, so print scores and hours are unchanged.
   - Place and the Links panel, Package (placed `.vectorcraft` documents packaged with their own linked files and fonts, relinked to the copies: #777), File Info, Print with print presets, PostScript output and print tiling, slices and Save for Web, Export for Screens and Asset Export, CSS Properties, PNG/PDF/SVG/text clipboard flavours; files copied in a file manager paste as art (SVG, PDF, EMF/WMF, bitmaps) on every desktop platform, and Linux/Wayland reads the compositor's clipboard (#398); on Linux the Paste menu checks the clipboard off the UI thread, so an X11 owner that never answers can't freeze the window (#510); screenshots and other copied pictures paste as embedded images at the view centre everywhere, the web included (#457).
+  - On the desktop, Copy and Cut make the system clipboard's formats (text, SVG, PDF, PNG) from a copy of the clipboard on the thread that writes background saves and exports, and write them when they are ready; while that thread has a save, an export, a print or a recovery copy to finish, they are made and written at once. Until they are written, Paste in VectorCraft takes the internal clipboard, and while a text field or the Type tool has the keyboard the app waits for them. Another Copy or Cut, or a copy of text in VectorCraft, drops them.
   - Missing linked files can be looked for in a folder and its subfolders: Find in Folder… in the Linked File Not Found dialog and in the Links panel menu lists the files with each one's name, those with the size and contents saved with the link first, and relinks the files chosen, copying an image's file into the document's folder when asked, without replacing a file there (`links.findFiles`, `links.relink {copy}`). In the Links panel it looks for the selected linked files when any are selected.
   - Linked files another app changes while their document is open follow Preferences › File Handling › Update Links, as they do when it opens: Automatically reads them again (an Update Links undo step), Ask When Modified offers to, Manually leaves them modified in the Links panel. The desktop app compares the active document’s linked files by size and modification time every two seconds and when its window comes back to the front, on a worker thread; a file still being written is tried again (`links.updateChanged`).
   - Import and paste, 2026-10-13: a multi-artboard `.ai` with notes beside its artboards opens from its editing data, a page's art past its artboard no longer lying over the page before it (#1528); a `.ai` gradient whose stops are listed upwards keeps each midpoint on the stop that starts its part of the ramp (#1530); SVG text on a path follows basic shapes (circle, ellipse, rect, line, polyline, polygon) as their SVG 2 equivalent paths (#1531, fixes #1527); PDFs whose alpha soft masks are drawn as images import with the mask instead of empty art (#1551); EPS and PostScript type set in Type 42 (TrueType) fonts imports at its size instead of 1000 times too large (#1553); PDF and EPS import keep a clipping path whose bounding box covers the page but whose shape doesn't (#1544, fixes #1542). Opening or placing a file with an image too large to decode says so, and the Links panel shows it on the row (#1540, part of #1479). Paste takes a PDF or EPS another app copied as editable vector art: from the macOS pasteboard (with SVG), EPS on Windows beside PDF, and `.eps` files copied in a file manager, with the new command `clipboard.importEps` (#1538, fixes #1499).