v1.1: fix transfer freeze, session tabs, per-panel toolbars, status bar

Freeze root cause: TransfersService consumed transferUpdate through an effect
that both read and wrote the jobMap signal — the first progress message spun
the effect into an infinite re-run loop, pegging the webview thread while the
copy completed fine bun-side. Push messages now flow through plain callback
registries on RpcService (also stops signal coalescing from dropping progress
snapshots). Verified live: a 60MB boot-time self-test copy streamed progress
into the running UI and the post-completion panel refreshes arrived.

- Tabs: workspaces (left+right PanelState pair each) in PanelsService; tab bar
  replaces the header; sessions persist in background tabs; Cmd+T/Cmd+W/Ctrl+Tab;
  closing a tab disconnects its sessions; last tab can't close
- Per-panel toolbar (top, icon-only): direction-explicit copy (-> / <-),
  rename, new folder/file, chmod, delete; panel footers removed
- VSCode-style status bar: transfer summary (spinner/percent/queued/failures,
  click to expand the job list) + active panel info; function bar removed
- transfer details list is collapsible, auto-expands on failure

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

ui/src/app/file-panel/file-panel.ts

@@ -34,6 +34,8 @@ export class FilePanel {
   readonly panel = computed(() => this.panels.get(this.side()));
   readonly isActive = computed(() => this.panels.activeSide() === this.side());
   readonly isRemote = computed(() => this.panel().sessionId() !== 'local');
+  /** The copy button points toward the other panel. */
+  readonly copyIcon = computed(() => (this.side() === 'left' ? 'mynaArrowRight' : 'mynaArrowLeft'));
 
   readonly pathDraft = signal('');
   readonly menuOpen = signal(false);
@@ -55,7 +57,17 @@ export class FilePanel {
   }
 
   activate(): void {
-    this.panels.activeSide.set(this.side());
+    this.panels.setActiveSide(this.side());
+  }
+
+  copyToOther(): void {
+    this.activate();
+    void this.transfers.copyToOtherPanel(this.side());
+  }
+
+  run(action: 'rename' | 'mkdir' | 'createFile' | 'chmod' | 'delete'): void {
+    this.activate();
+    this.actions[action](this.panel());
   }
 
   pickLocal(): void {
@@ -129,7 +141,7 @@ export class FilePanel {
 
     if (key === 'Tab') {
       event.preventDefault();
-      this.panels.activeSide.set(this.panels.otherSide(this.side()));
+      this.panels.setActiveSide(this.panels.otherSide(this.side()));
       return;
     }
     if ((event.metaKey || event.ctrlKey) && key.toLowerCase() === 'a') {
@@ -171,17 +183,17 @@ export class FilePanel {
         panel.up();
         break;
       case 'F2':
-        this.actions.rename();
+        this.actions.rename(panel);
         break;
       case 'F5':
-        void this.transfers.copyToOtherPanel();
+        void this.transfers.copyToOtherPanel(this.side());
         break;
       case 'F7':
-        this.actions.mkdir();
+        this.actions.mkdir(panel);
         break;
       case 'F8':
       case 'Delete':
-        this.actions.delete();
+        this.actions.delete(panel);
         break;
       default:
         return; // let unhandled keys through