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/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.