P1: typed RPC bridge + FileSystemProvider + dual-panel local browsing

- shared/types + shared/rpc: full wire contract (Result envelope, no exceptions cross the bridge)
- FileSystemProvider interface, LocalProvider, SessionRegistry with built-in 'local'
- walk.ts: provider-generic recursive walk + removeRecursive
- rpc-handlers wired into BrowserWindow; 10min request timeout for slow SFTP ops
- Angular: RpcService (Electroview bridge + plain-browser guard), PanelsService with
  signals-based PanelState (sort/cursor/selection), FilePanel component with
  keyboard nav (arrows/Space/Enter/Backspace/Tab), path bar, toasts
- verified: both panels listDir home over the bridge in the running app

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/index.ts

@@ -1,5 +1,7 @@
 import { BrowserWindow, Updater } from "electrobun/bun";
 import { BRANDING } from "../shared/branding";
+import { SessionRegistry } from "./fs/registry";
+import { createAppRPC } from "./rpc-handlers";
 
 const PROD_URL = "views://app/index.html";
 
@@ -21,9 +23,11 @@ async function getMainViewUrl(): Promise<string> {
 	}
 }
 
+const registry = new SessionRegistry();
+const rpc = createAppRPC(registry);
 const url = await getMainViewUrl();
 
-const mainWindow = new BrowserWindow({
+new BrowserWindow({
 	title: BRANDING.appName,
 	url,
 	frame: {
@@ -32,6 +36,7 @@ const mainWindow = new BrowserWindow({
 		x: 120,
 		y: 120,
 	},
+	rpc,
 });
 
 console.log(`${BRANDING.appName} started (${url})`);