feat(ui): hide monitor panel by default and reduce width

- Remove auto-open of monitor panel on startup
- Reduce monitor panel width from 500px to 320px

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/web/public/app.js

@@ -55,8 +55,6 @@ class ClaudemanApp {
     this.loadState();
     this.loadQuickStartCases();
     this.setupEventListeners();
-    // Show monitor panel by default
-    this.toggleMonitorPanel();
     // Start system stats polling
     this.startSystemStatsPolling();
   }