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>

README.md

@@ -25,10 +25,8 @@ remote server over SSH/SFTP, so you can move files **local↔remote**,
   (MB/s or Mbps), persisted across restarts.
 - On macOS the tab bar is fused with the window titlebar; other platforms keep
   a standard titlebar.
-- **Menu-bar (tray) icon**: template icon that adapts to light/dark; during
-  transfers it fades and fills an aggregate progress bar (delivered/total bytes
-  of the whole queue). Its menu lists your tabs with live per-tab transfer
-  info — click one to jump to it — plus Show and Quit.
+- **Menu-bar (tray) icon**: template icon that adapts to light/dark; click it
+  to bring the app to the front.
 - **Edit files** (F4 / toolbar / File menu): a built-in editor works on local
   and remote files directly; or pick an external app (Options → Editor →
   Custom → Choose…). External edits of remote files download to a temp folder,