fix(ui): monitor panel off by default; unbreak task-badge open when hidden

Fresh desktop installs slid the Monitor panel open at startup — the two
showMonitor fallbacks defaulted to true (mobile already defaulted false
via getDefaultSettings). Default it to false everywhere; users opt in
via App Settings -> Show Monitor.

Also fix toggleMonitorPanel(): applyMonitorVisibility() leaves inline
display:none when the setting is off, so the session-tab task badge
toggled the open class invisibly (already broken on mobile). Clear the
inline display when opening so transient opens work.

Local echo defaults audited, unchanged: off on desktop, on for touch
(?? MobileDetection.isTouchDevice()), stored per-device and never
server-synced.

Verified on a fresh isolated instance (desktop + iPhone 13 emulation):
14/14 checks — panel closed + checkbox unchecked on both device
classes, local echo desktop-off/mobile-on, separate storage keys,
badge open works.

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

src/web/public/panels-ui.js

@@ -380,6 +380,9 @@ Object.assign(CodemanApp.prototype, {
     panel.classList.toggle('open');
 
     if (panel.classList.contains('open')) {
+      // applyMonitorVisibility() sets inline display:none when the "Show Monitor"
+      // setting is off — clear it so transient opens (session-tab task badge) work
+      panel.style.display = '';
       // Load screens and start stats collection
       await this.loadMuxSessions();
       await fetch('/api/mux-sessions/stats/start', { method: 'POST' });