Symbols: Edit Symbol opens the symbol in its own editing mode, and every instance follows each edit

Squashed from #5064 onto main.

docs/mcp.md

@@ -1568,7 +1568,12 @@ already walks Image Trace. Short agent entry points:
   9-slice guides on or off; `nineSliceGuides` is `[left, top, right, bottom]`, fractions 0..1 of the symbol size; rows
   of `symbol.list` carry `nineSlice`: the guides or `null`; `type` is Symbol Type, `static` by default for the command
   and `dynamic` by default in the Symbol Options dialog),
-  `symbol.place {name?, x?, y?}`, `symbol.breakLink {ids?}`, `symbol.replace`, `symbol.edit`, `symbol.duplicate`,
+  `symbol.place {name?, x?, y?}`, `symbol.breakLink {ids?}`, `symbol.replace`,
+  `symbol.edit {id?, name?, x?, y?, artboard?, viewCenter?}` (symbol editing mode: the symbol's art on a temporary
+  isolated layer, where the instance `id` shows it or centered on (x, y), by default on the center of artboard
+  `artboard`, the active one the app passes, or in a document without artboards on `viewCenter`, the view's center the
+  app passes; every instance follows each edit and stays linked), `symbol.exitEditing`
+  (leaves the mode; without an edit it adds no undo step), `symbol.duplicate`,
   `symbol.selectInstances {name}`, `symbol.delete {name | names, expandInstances?}` (`names` deletes several in one
   undo step). `symbol.new` and `symbol.duplicate {name, newName?}` trim the white space around the
   name they are given, as `symbol.options` trims `newName`; a blank one gives "New Symbol" or "<name> copy".
@@ -1580,8 +1585,8 @@ already walks Image Trace. Short agent entry points:
   0..100 and `blend` a blend mode name; `null` gives one back to the symbol. It is refused for a static symbol and for
   a path that names no object. `symbol.instance.reset {ids?}` drops the selected instances' changes (the Properties
   panel's Reset). Redefining the symbol (`symbol.update`) reshapes every instance and keeps each change whose path the
-  new art still has; `symbol.breakLink` bakes the changes into the expanded art; `symbol.edit` expands the symbol's own
-  art; making the symbol static drops them.
+  new art still has; `symbol.breakLink` bakes the changes into the expanded art; `symbol.edit` edits the symbol's own
+  art, and each edit there keeps the changes whose path the art still has; making the symbol static drops them.
 
 ```json
 {"name":"run_command","arguments":{"command":"symbol.instance.setAppearance","params":{"id":42,"path":[1],"fill":"#d0021b","opacity":80}}}

docs/target-app-parity.md

@@ -606,6 +606,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - macOS: Finder opens every format File › Open reads with VectorCraft (double-click, Open With, a drop on the Dock icon, `open -a`), at launch or while it runs; the release and `cargo xtask bundle` apps share one `Info.plist` that declares those document types, owning only VectorCraft's own formats. The DMG opens on a designed Finder window, VectorCraft.app beside the `Applications` link over a background with the app icon (#493).
   - Swatch and graphic style libraries, Libraries panel files, presets and plug-ins open wherever they are dropped on the window, as File › Open opens them.
   - **Symbol libraries** ([public source](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/create-or-import-symbol-libraries.html)): Window › Symbol Libraries and the Symbols panel's Symbol Libraries Menu open each library in a library panel of its own, as swatch and graphic style libraries do. The built-in library, Basic Shapes, is original art generated in code (`crates/engine/src/cmd/symbollib.rs`). A click on a symbol adds it to the document's Symbols as one undo step, with its Symbol Options (size, registration, export type, 9-slice guides) and every resource it uses (the symbols it nests, patterns, swatches, brushes, graphic styles, images), and makes it the current symbol; a symbol the document already has is not added again and another symbol of the same name keeps its name, the library's comes in numbered. Thumbnails, in the library panels and the Symbols panel, draw a symbol with the symbols it nests and the patterns and images it uses. Dragging a library symbol onto the canvas also places an instance there, in the same step ([placing from a library](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/create-and-place-symbols.html)). Save Symbols (the library menu) and Save Symbol Library… (the Symbols panel menu) write the document's symbols as a `.vectorcraft` document holding only them, into the user library folder (listed under User Defined) or a file; Other Library… reads the symbols of any document VectorCraft opens; a file it can't read is an error and opens no panel. Tests: `crates/engine/src/tests/symbollib.rs`, `crates/ui-egui/src/panels/tests_symbol_libraries.rs`, `panels::symbols::tests::thumbnails_show_the_symbols_a_symbol_nests`, `canvas::tests::a_library_symbol_dropped_on_the_canvas_is_added_and_placed_there_in_one_step`.
+  - **Symbol editing mode** ([Edit symbols](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/edit-symbols.html), [Symbols panel options](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/symbols-panel-options.html)): a double-click on a symbol instance, the Control bar's Edit Symbol button, a double-click on a symbol in the Symbols panel and the panel menu's Edit Symbol (`symbol.edit`) open the symbol's art on a temporary isolated layer, where the instance shows it (from the panel: centered on the active artboard, or in the view in a document without artboards), with the rest of the document dimmed. Each edit there changes every instance at once; the instances keep their own transforms and stay linked (Break Link to Symbol still expands one), and a dynamic symbol's instances keep their appearance changes to the objects the art still has. Escape, the isolation bar's back button, the Control bar's Exit Symbol Editing Mode and a double-click outside the art leave the mode (`symbol.exitEditing`); leaving without an edit adds no undo step. Saving leaves the editing layer out. Tests: `crates/engine/src/tests/symboledit.rs`, `select::tests::a_double_click_on_a_symbol_instance_edits_its_symbol`, `panels::symbols::tests::edit_symbol_from_the_panel_centers_the_art_on_the_active_artboard_or_the_view`.
   - **Delete Symbol asks first** ([Symbols panel](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/symbols-panel-options.html), [symbol libraries](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/create-or-import-symbol-libraries.html), [Alt-click Delete](https://helpx.adobe.com/illustrator/using/default-keyboard-shortcuts.html)): the Symbols panel's Delete Symbol button and menu item ask "Delete the selected symbol?" with Yes and No for a symbol no instance uses. For a symbol with placed instances they ask with Expand Instances (the instances become ordinary art), Delete Instances and Cancel; either Instances button deletes the symbol in one undo step. Alt-click on the button deletes an unused symbol without asking and still asks about one with instances. A question left open while another document became active deletes nothing. `symbol.delete` itself does not ask. Tests: `panels::symbols::tests::delete_symbol_asks_first_and_alt_click_deletes_an_unused_symbol_at_once`, `the_in_use_question_expands_or_deletes_the_instances`, `a_stale_delete_symbol_question_deletes_nothing`, `the_delete_symbol_questions_show_their_buttons`.
   - **Symbols › Select All Unused** ([Symbols panel](https://helpx.adobe.com/illustrator/desktop/manage-objects/traces-mockups-symbols/symbols-panel-options.html), #4918): the Symbols panel menu's Select All Unused shows the symbols nothing places selected (`symbol.unused`): instances in the art (opacity masks included), graph designs, pattern tiles and brush art count, and so do instances in a used symbol's art. Delete Symbol, the button or the menu item, then asks "Delete the selected symbols?" once and deletes those still unused in one undo step (`symbol.delete {names}`); Alt-click on the button deletes them without asking, and a click on a symbol picks just it again. Tests: `tests::brushsym::symbol_unused_lists_the_symbols_nothing_places_and_delete_takes_several`, `panels::symbols::tests::select_all_unused_picks_the_unused_symbols_and_delete_deletes_them`, `dialogs::symbol_delete::tests::several_symbols_get_the_plural_question`.
   - **Brush libraries** ([public source](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/apply-and-edit-strokes/create-new-brush-libraries.html), [import](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/apply-and-edit-strokes/import-brushes-from-brush-libraries-or-other-files.html), [Brushes panel](https://helpx.adobe.com/illustrator/desktop/paint-and-fill/apply-and-edit-strokes/brushes-panel-overview.html)): Window › Brush Libraries, the Brushes panel's Brush Libraries Menu and its menu's Open Brush Library open each library in a library panel of its own, as swatch, graphic style and symbol libraries do. The built-in libraries (Art Ribbons, Calligraphic Nibs, Pattern Borders, Scatter Shapes) are original brushes generated in code (`crates/engine/src/cmd/brushlib.rs`); Striped Ribbon's art is filled with the library's own pattern and Sparkles scatters the library's own symbol. A click on a brush adds it to the document's Brushes as one undo step with every resource its art uses (patterns, symbols, swatches, graphic styles, images), makes it the current brush and, with paths selected, applies it to them in the same step; a brush the document already has is not added again and a different brush of the same name comes in numbered ("Wave 2"). Shift/Cmd-clicks select brushes for Add to Brushes; a brush dragged onto a path is added and applied to it, and one dragged onto the Brushes panel is added. Save Brushes… / the Brushes panel's Save Brush Library… write the document's brushes (or the selected ones) as a `.vectorcraft` library into the `Brushes` folder next to the preferences, listed under User Defined, or to a file; Other Library… reads the brushes of any document VectorCraft opens. Thumbnails, in the library panels, the Brushes panel and Brush Options, render brush art with the patterns and symbols it uses. Copying brushed art now carries the patterns and symbols its brush's art uses too. Tests: `crates/engine/src/tests/brushlib.rs`, `crates/ui-egui/src/panels/tests_brush_libraries.rs`, `panels::brushes::tests::library_brush_previews_show_the_patterns_their_art_uses`, `canvas::tests::a_library_brush_dropped_on_a_path_is_added_and_applied_in_one_step`.