feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/libs/stream-monaco/todo.md

@@ -0,0 +1,27 @@
+# TODO
+
+## Current Focus
+
+- [x] Keep shrinking `src/core/DiffEditorManager.ts` only where the next slice is low-coupling and behavior-preserving.
+- [x] Extract unchanged-region reveal button wiring and bridge wheel handling into helpers.
+- [x] Extract the remaining center activation / click-flow glue into helpers if it can stay stateless.
+- [x] Re-evaluate the unchanged-region area after each slice and stop once the remaining code is mostly orchestration.
+
+## Validation Plan
+
+- [x] Run `pnpm lint`.
+- [x] Run `pnpm typecheck`.
+- [x] Run targeted unchanged-region presentation tests first.
+- [x] Run the full `pnpm vitest run` suite after each landed slice.
+
+## Remaining Follow-ups
+
+- [x] Decide whether `DiffEditorManager` should stop here or split one level further by responsibility.
+- [ ] Keep `src/index.base.ts` as orchestration only and avoid reintroducing editor update logic there.
+- [ ] If a future unchanged-region feature touches this area again, prefer another stateless DOM/helper slice before growing `DiffEditorManager` in place.
+- [x] Audit `clearHighlighterCache()` semantics against the other shared highlighter state.
+- [x] Align `README.md`, `package.json`, `CHANGELOG.md`, and release workflow version story.
+- [x] Add at least one Playwright smoke job to CI.
+- [x] Add at least one real framework example (`React` or `Vue`) to match the package positioning.
+- [x] Verify package side-effect metadata against the automatic worker hook behavior.
+- [x] Verify the build target / platform choices and document the reason if they stay as-is.