Add built-in auto-updater with tab-bar update pill

Wires electrobun's Updater to the /dl download host. The packaged app checks
https://miniscp.com/dl on launch + every 6h; when a newer build exists, an
accent-colored "update tool" appears next to Connections in the tab bar. It
announces the update, becomes its own inline progress bar while downloading,
then flips to "Restart to apply" (two-step: download, then user-triggered
relaunch).

- electrobun.config.ts: release.baseUrl = https://miniscp.com/dl (baked into
  version.json at build; miniscp.com fronted by an external proxy for TLS).
- rpc.ts: checkForUpdate/downloadUpdate/applyUpdate requests + updateStatus push.
- rpc-handlers.ts + index.ts: call Updater; poll on launch+6h; stream
  onStatusChange progress. checkForUpdate self-guards the dev channel.
- rpc.service.ts + new updater.service.ts: signal-based state
  (available -> downloading -> ready, ready derived from downloadUpdate ok).
- tab-bar.ts: single bg-primary pill; progress fills the pill itself.
- icons.ts: register mynaDownload. i18n: tabBar + menu keys across all locales.
- menu.ts + app.ts: "Check for Updates…" app-menu item -> UpdaterService.check().
- docs: build-and-release + architecture updated.

Unsigned builds still update (applyUpdate strips the macOS quarantine xattr).
Verified: tsc --noEmit (exit 0) + build:ui AOT (exit 0). Live pill + full
download/apply flow require a two-build test on the host.

Co-Authored-By: Claude <noreply@anthropic.com>

docs/build-and-release.md

@@ -88,9 +88,33 @@ internal box (plain HTTP `:80`, no domain/TLS). Deploys to `/srv/miniscp/`.
 - `site/deploy.sh` — run per build machine after `scripts/release.ts`; copies `artifacts/stable-*`
   and renames the build-numbered win portable zip to the stable `stable-win-x64-miniSCP-portable.zip`.
   `MINISCP_DL_DIR` overrides the target (stage locally, then rsync to the server).
-- **Future updater** (not wired yet): set `release.baseUrl = http://<host>/dl/` in
-  `electrobun.config.ts` (currently unset) → builds start emitting `.patch` files that `deploy.sh`
-  already ships. Then call the electrobun `Updater` API on launch/interval/tray.
+- `release.baseUrl = https://miniscp.com/dl` is set in `electrobun.config.ts`; `miniscp.com` is
+  fronted by an external proxy for TLS (Caddy itself stays on `:80` behind it). The value is baked
+  into `version.json` at build time, so only builds made after it was added check for updates.
+  With `generatePatch` (default true), release builds now need **build-time network to
+  `miniscp.com/dl`** so electrobun can fetch the currently-published version to diff a `.patch`
+  (the first build after enabling it has nothing to diff and just ships the full artifacts).
+
+## Auto-updater (app side)
+
+Wired on top of the download host above. See the "Auto-updater" section in
+[architecture.md](architecture.md) for the runtime flow.
+
+- **Backend** ([src/bun/index.ts](../src/bun/index.ts)): `Updater.checkForUpdate()` runs ~5s after launch and
+  every 6h; on `updateAvailable` it pushes `rpc.send.updateStatus({phase:"available",…})`.
+  `Updater.onStatusChange` streams `download-progress` (0–100) → `updateStatus{downloading}`.
+  `checkForUpdate` self-guards the `dev` channel, so `bun run dev` never shows the pill.
+- **RPC** ([src/shared/rpc.ts](../src/shared/rpc.ts)): requests `checkForUpdate` / `downloadUpdate` /
+  `applyUpdate` (handlers in [rpc-handlers.ts](../src/bun/rpc-handlers.ts) call the electrobun `Updater`);
+  push message `updateStatus`.
+- **UI**: `UpdaterService` ([ui/src/app/updater.service.ts](../ui/src/app/updater.service.ts)) holds signals
+  (`state`/`version`/`progress`); the tab-bar "update pill" ([tab-bar.ts](../ui/src/app/tab-bar/tab-bar.ts))
+  is one accent (`bg-primary`) control that announces → fills as a progress bar while downloading →
+  "Restart to apply". `state` is `available → downloading → ready` (ready derived from the
+  `downloadUpdate` response). App-menu "Check for Updates…" ([menu.ts](../src/bun/menu.ts)) routes a
+  `check-for-updates` menu action into `UpdaterService.check()`.
+- **Unsigned is fine:** `applyUpdate()` strips the macOS quarantine xattr before relaunch, so the
+  swapped bundle isn't Gatekeeper-blocked.
 
 ## Icons