Update Tauri migration documentation and scaffold

docs/tauri-migration.md

@@ -7,6 +7,8 @@ References checked during the spike:
 - Tauri Vite setup: https://v2.tauri.app/start/frontend/vite/
 - Tauri JavaScript API: https://v2.tauri.app/reference/javascript/api/
 - Tauri CLI: https://v2.tauri.app/reference/cli/
+- Tauri dialog plugin: https://v2.tauri.app/plugin/dialog/
+- Tauri opener plugin: https://v2.tauri.app/plugin/opener/
 
 ## Current Electron Responsibilities
 
@@ -14,12 +16,12 @@ References checked during the spike:
 | --- | --- | --- |
 | Main app window | `BrowserWindow` in `electron/main.cjs`, loading Vite in dev and `dist/index.html` in production | `src-tauri/tauri.conf.json` window loading the same Vite dev URL or `../dist` |
 | Settings window | Separate modal `BrowserWindow` routed to `#/settings` | Later phase: either a second Tauri webview window or in-app settings route |
-| Settings persistence | JSON file under Electron `app.getPath('userData')`, with migrations and normalization | Later phase: Tauri command backed by app config/data dir with the same setting keys and migrations |
-| Renderer bridge | `electron/preload.cjs` exposes `window.electronAPI`; renderer uses `src/desktop/desktopApi.js` | `desktopApi` can call Tauri commands through `window.__TAURI__.core.invoke` when running in Tauri |
-| File picker | `dialog.showOpenDialog` via `pick-paths` IPC | Later phase: official Tauri dialog plugin with scoped permissions |
-| Open file/path | `shell.openPath` via `open-path` IPC | Later phase: official Tauri opener plugin or a scoped Rust command |
-| External links | `shell.openExternal` and `setWindowOpenHandler` | Later phase: official Tauri opener plugin and window navigation policy |
-| Window focus events | Electron `focus` event forwarded to renderer | Later phase: Tauri window event listener or emitted command event |
+| Settings persistence | JSON file under Electron `app.getPath('userData')`, with migrations and normalization | Implemented for Tauri with `HEIMGEIST_SETTINGS_FILE` override or app config `settings.json`; keys and normalizers mirror Electron closely |
+| Renderer bridge | `electron/preload.cjs` exposes `window.electronAPI`; renderer uses `src/desktop/desktopApi.js` | Implemented: `desktopApi` still prefers Electron and falls back to Tauri commands/listeners |
+| File picker | `dialog.showOpenDialog` via `pick-paths` IPC | Implemented for Tauri through the official dialog plugin; supports existing `title` and `filters` options |
+| Open file/path | `shell.openPath` via `open-path` IPC | Implemented for Tauri through the official opener plugin |
+| External links | `shell.openExternal` and `setWindowOpenHandler` | Implemented for Tauri through the official opener plugin for `http`, `https`, `mailto`, and `tel` URLs |
+| Window focus events | Electron `focus` event forwarded to renderer | Implemented for Tauri by emitting `window-focused` and listening from `desktopApi` |
 | App menu | Electron `Menu.buildFromTemplate` | Later phase: Tauri menu API |
 | UI scale | Electron `webContents.setZoomFactor` | Later phase: Tauri/webview equivalent or renderer CSS scale strategy |
 | DevTools preference | Electron opens/closes DevTools in dev | Later phase: Tauri devtools behavior and persisted preference |
@@ -30,8 +32,8 @@ References checked during the spike:
 ## Scaffold Added
 
 - `src-tauri/tauri.conf.json` points Tauri at the existing Vite renderer on `http://127.0.0.1:5173` and the existing `dist` build output.
-- `src-tauri/src/main.rs` registers placeholder Tauri commands that match the current `desktopApi` surface.
-- `src-tauri/capabilities/default.json` grants the main window the default core capability for this spike.
+- `src-tauri/src/main.rs` registers Tauri commands for settings, file picking, path opening, external link opening, focus events, and update placeholders.
+- `src-tauri/capabilities/default.json` grants the main window core, dialog, and opener permissions used by this spike.
 - `src-tauri/icons/icon.png` is a placeholder icon required by Tauri context generation.
 - `src/desktop/desktopApi.js` still prefers Electron. When Electron is absent and Tauri is present, it invokes matching Tauri commands. Without either desktop bridge, it falls back to safe defaults so the renderer can mount.
 
@@ -46,15 +48,14 @@ References checked during the spike:
 
 - No Electron files, scripts, or IPC behavior were removed.
 - No Python backend sidecar, packaging, or lifecycle work was added.
-- No Tauri updater, opener, dialog, menu, or settings persistence parity was implemented.
-- The Tauri settings command is in-memory only and exists to let the renderer hydrate during the spike.
+- No Tauri updater, app menu, second settings window, UI zoom side effects, DevTools preference side effects, or packaging parity was implemented.
+- No Python backend sidecar or packaging work was added.
 
 ## Remaining Parity Gaps
 
-- Settings: persistent storage, migrations, normalization, UI scale side effects, DevTools preference side effects.
-- File picker: native picker and path filters.
-- Open path and external links: scoped native opener behavior.
-- Window focus events: renderer notification equivalent.
+- Settings: UI scale side effects and DevTools preference side effects are not wired in Tauri yet.
+- Settings window: Electron still has a separate modal settings window; Tauri currently uses the existing renderer route only.
+- App menu: Electron menu roles are not recreated in Tauri.
 - Update flow: startup/manual checks, changelog, restart, and signed release strategy.
 - Backend lifecycle: FastAPI startup, health gating, ffmpeg/ffprobe environment, shutdown, and sidecar packaging.
 - Packaging: bundle metadata, icons, signing/notarization, auto-update channel, and platform install behavior.