Swatches: swatch exchange (.ase) files open as swatch libraries

File › Open, Other Library… and the User Defined library folder read
.ase files. Colors keep their model, global and spot colors stay global
and spot, and color groups stay groups. The library readers take a
file's bytes. On the web, File › Open passes a swatch library file to
swatch.library.load as dataBase64 instead of as lossy UTF-8 text.

Swatch and group names in a library are now unique, in .gpl files too.
Add to Swatches puts each color group of a library into one document
group when the document already has a swatch with the group's name.
The library fuzz helpers fail when a command panics.

docs/control-protocol.md

@@ -154,7 +154,7 @@ Clicking a swatch there runs `swatch.library.add {library, names: [name], apply}
 one with Alt), so one undo step adds and applies it; Shift/Cmd-clicks select swatches and colour groups for
 Add to Swatches.
 `window.swatchLibrary.other {path?}` loads a library file (or another document's swatches) and opens it there;
-opening a `.vcswatches` or `.gpl` file with `app.open` does the same. `ui.saveSwatchLibrary {names?}` opens the
+opening a `.vcswatches`, `.gpl` or `.ase` file with `app.open` does the same. `ui.saveSwatchLibrary {names?}` opens the
 `saveSwatchLibrary` dialog (fields `name`, `format`: `vcswatches`/`gpl`/`css`, `user`: save to the user library
 folder, `selectedOnly` with `names`); `ui.dialog.confirm` runs `swatch.library.save` (to a file it asks for a path).
 

docs/development.md

@@ -238,7 +238,7 @@ web build has no net at all.
 Untrusted input has property tests that must never panic:
 
 - `crates/engine/tests/import_fuzz.rs`: garbage, hostile and mutated SVG and PDF, and swatch
-  (`.vcswatches`, `.gpl`), graphic style (`.vcstyles`) and flattener preset (`.vcflattener`)
+  (`.vcswatches`, `.gpl`, `.ase`), graphic style (`.vcstyles`) and flattener preset (`.vcflattener`)
   libraries, loaded and used, then rendered and exported.
 - `crates/engine/tests/command_sweep.rs`: every command with junk parameters.
 - `crates/format/tests/prop_format.rs`: garbage and mutated `.vectorcraft` files.

docs/mcp.md

@@ -740,7 +740,9 @@ swatch in the library panel does). `swatch.resetDefaults {replace?}` brings back
 as a library (`.vcswatches` keeps colour models, global, spot, gradients and colour groups; `.gpl` is 8-bit RGB;
 CSS writes custom properties); without `path` it returns `{data}`, and `user: true` saves into the user library
 folder of the desktop app (listed as category `user`, User Defined). `swatch.library.load {path? | data? |
-dataBase64?, name?}` loads a `.vcswatches` or `.gpl` file, or another document's swatches, as a library to add from.
+dataBase64?, name?}` loads a `.vcswatches`, `.gpl` or swatch exchange (`.ase`) file, or another document's swatches,
+as a library to add from. From an `.ase` file it reads RGB, CMYK, Lab and Gray colors as global, spot or process
+swatches and keeps their color groups.
 
 ## Graphic style libraries