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>

src/shared/rpc.ts

@@ -157,6 +157,16 @@ export type AppRPC = {
 			managerConnect: { params: { id: string }; response: Result };
 			managerOpenStack: { params: { id: string }; response: Result };
 			managerClose: { params: Record<string, never>; response: Result };
+			// auto-updater (electrobun Updater)
+			/** Main window: re-run the update check on demand (menu item). */
+			checkForUpdate: {
+				params: Record<string, never>;
+				response: Result<{ updateAvailable: boolean; version: string }>;
+			};
+			/** Download the pending update (patch-chain, else full). Progress arrives via updateStatus. */
+			downloadUpdate: { params: Record<string, never>; response: Result };
+			/** Swap in the downloaded update and relaunch — quits the app, so may not resolve. */
+			applyUpdate: { params: Record<string, never>; response: Result };
 		};
 		messages: {
 			/** Editor → bun draft mirror; safety net for the non-cancellable native close. */
@@ -179,6 +189,16 @@ export type AppRPC = {
 			managerState: { open: boolean };
 			/** bun → main: the manager window changed the connection store. */
 			connectionsChanged: Record<string, never>;
+			/**
+			 * bun → main: auto-updater lifecycle, drives the tab-bar update pill.
+			 * "ready" is not a phase — the UI derives it from downloadUpdate resolving ok.
+			 */
+			updateStatus: {
+				phase: "available" | "downloading" | "error";
+				version?: string;
+				progress?: number;
+				error?: string;
+			};
 		};
 	};
 };