Refactor the TypeScript data flow for full type safety and auto-generation of Rust types (#3865)

* Migrate Specta to Tsify to auto-generate messages.ts, working except colors and widgets

* Adopt the generated FillColor/Color/GradientStops

* Fix widget typing

* Separate WidgetGroup enum variants into wrapper structs

* Small rename

* Simplify widgets further

* Clean up message type references

* Switch type imports to the auto-generated file

* Remove lowercase serde rename

* Fix FillChoice deserialization

* Fix small regression from #3837

* Improve type safety

* Make WidgetSpan type-safe

* More cleanup and type safety

* More type safety

* More type safety

* Get the rest to type-check without errors; improve widget builder macro to have optional icons; improve Svelte 5 configs

* Cargo fmt

* Fix imports

* Update outdated readme info

* Fix lint command rename references

* Fix typos

* One more typos fix

* Remove unnecessary dep: prefix from the edited Cargo.toml files

* Remove excess parts from Cargo.toml

* Fix compiling on desktop

* Revert "Remove excess parts from Cargo.toml"

This reverts commit 6b711117b3a5d5d8a3ee20f36a43bc74930b7c82.

* Update dev docs with simpler, more accurate instructions

frontend/src/components/README.md

@@ -1,6 +1,6 @@
 # Overview of `/frontend/src/components/`
 
-Each component represents a (usually reusable) part of the Graphite editor GUI. These all get mounted in `Editor.svelte` (in the `/src` directory above this one).
+Each component represents a (usually reusable) part of the Graphite editor GUI.
 
 ## Floating Menus: `floating-menus/`
 
@@ -12,7 +12,11 @@ Useful containers that control the flow of content held within.
 
 ## Panels: `panels/`
 
-The dockable tabbed regions like the Document, Properties, Layers, and Node Graph panels.
+The dockable tabbed regions like the Document, Properties, Layers, Data, and Welcome panels.
+
+## Views: `views/`
+
+Content views rendered within panels, such as the node graph.
 
 ## Widgets: `widgets/`