Simplify tray: static template icon, click focuses the app

The setImage-swapped progress frames lost the template treatment on macOS and
rendered black-on-dark once transfers started. Dial back per user decision:
the tray is now just the glyph (template image set once at construction, never
swapped) and clicking it activates the window — no menu, no progress effects.
Removes everything that only served the fancy version: progress frames +
generation, engine.aggregateProgress, the workspacesSync webview->bun channel
(schema, send proxy, panels effect, handlers) and the activate-tab action.

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

ui/src/app/rpc.service.ts

@@ -87,20 +87,4 @@ export class RpcService {
     });
   }
 
-  /** Fire-and-forget messages to the bun process (e.g. workspacesSync). */
-  get send() {
-    const rpc = this.rpc;
-    if (!rpc) throw new Error('RPC is only available inside the desktop app');
-    const ready = this.ready;
-    return new Proxy({} as (typeof rpc)['send'], {
-      get:
-        (_target, message: string) =>
-        (payload?: unknown) => {
-          void ready.then(() => {
-            const messages = rpc.send as unknown as Record<string, (p?: unknown) => void>;
-            messages[message](payload);
-          });
-        },
-    });
-  }
 }