feat(app): panel zoom — full-grid render + header toggle

Wire Cmd::SetZoom through Tauri bridge (set_zoom command), add zoomed
field to WorkspaceView, short-circuit LayoutEngine to render only the
zoomed panel full-grid, and toggle Maximize2/Minimize2 in panel header.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/socketBridge.ts

@@ -181,3 +181,7 @@ export interface DaemonHealth { version: string; pid: number; started_at_ms: num
 export async function getHealth(): Promise<DaemonHealth> {
   return await invoke<DaemonHealth>("health");
 }
+
+export async function setZoom(workspaceId: string, surfaceId: string | null): Promise<void> {
+  await invoke("set_zoom", { workspaceId, surfaceId });
+}