M10.2: Tauri v2 desktop scaffold (desktop/) — Vue frontend as the webview

New desktop/ Tauri v2 project (Linux-first, cross-platform-ready):
- src-tauri: Cargo.toml (lib + thin main.rs shim), build.rs, lib.rs (Builder
  entry point), tauri.conf.json (frontendDist -> ../../frontend/dist, devUrl
  :5173, deb+appimage bundles), capabilities/default.json (core:default),
  .gitignore.
- The shared Vue 3 frontend is the sibling ../frontend; before-commands cd via
  "$(git rev-parse --show-toplevel)/frontend" since frontend and src-tauri are
  siblings, not nested.
- Icons generated from frontend/public/icon.svg via `cargo tauri icon` in CI
  (M10.8), not committed.

Boots the shared UI in a native window. The local data adapter (M10.3/M10.5)
and CI build verification (M10.8) follow. desktop/** is not yet in the CI paths
filter — added with the desktop lane in M10.8.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

desktop/README.md

@@ -0,0 +1,61 @@
+# ThoughtSync desktop (Tauri v2)
+
+Local-first desktop client. The window loads the shared **Vue 3 frontend** from
+`../frontend`; the Rust core (`src-tauri`) owns the on-device store and the opt-in
+sync engine (built out across the M10 milestone). Works fully offline; optionally
+syncs to a self-hosted ThoughtSync server.
+
+## Layout
+
+```
+desktop/
+  src-tauri/
+    Cargo.toml
+    build.rs
+    tauri.conf.json          # frontendDist -> ../../frontend/dist, devUrl :5173
+    capabilities/default.json
+    src/
+      main.rs                # thin shim -> lib::run()
+      lib.rs                 # tauri::Builder entry point
+```
+
+The Vue frontend is the sibling `../frontend` package, **shared with the web
+build**. On desktop it is backed by a local data source via
+`frontend/src/adapters/` (M10.3) instead of the server REST API. `frontend` and
+`src-tauri` are **siblings, not nested**, so the `beforeDev`/`beforeBuild`
+commands `cd "$(git rev-parse --show-toplevel)/frontend"` to resolve regardless of
+the CLI's working directory.
+
+## Prerequisites
+
+The toolchain (Rust + Node + WebKitGTK 4.1 + `tauri-cli`) is provided by the
+`ci-tauri` CI image. For local dev: install Rust + Node, `cargo install tauri-cli`,
+and the Tauri v2 Linux system deps — see `CI-tauri/Dockerfile` in the CI-runner
+repo for the exact apt list (libwebkit2gtk-4.1-dev, libgtk-3-dev, librsvg2-dev,
+libayatana-appindicator3-dev, libxdo-dev, patchelf, ...).
+
+## Dev
+
+```sh
+cd desktop/src-tauri && cargo tauri dev
+```
+
+`beforeDevCommand` starts the Vite dev server (port 5173) in `../frontend`.
+
+## Build (Linux)
+
+```sh
+cargo tauri icon "$(git rev-parse --show-toplevel)/frontend/public/icon.svg"
+cd desktop/src-tauri && cargo tauri build   # -> .deb + .AppImage
+```
+
+App icons are **generated** from the frontend's `icon.svg` via `cargo tauri icon`
+(not committed; CI does this before `cargo tauri build`). Bundle targets: `deb`,
+`appimage` (Linux-first; Windows/macOS later, no code changes expected).
+
+## Status
+
+Scaffold (M10.2): boots the shared Vue UI in a native window. Until the local data
+adapter lands (M10.3 + M10.5) the app has no server configured, so it shows the
+login screen without a working backend — full offline functionality arrives with
+the local SQLite store (M10.4) + `adapters/local.ts` (M10.5).