feat: use Task tool description for subagent window titles + auto-minimize completed

- Extract short description from TaskTracker (params.description) for subagent windows
- Correlate subagents with sessions by working directory and timing
- Auto-minimize subagent windows when agents complete
- Persist minimized/open window states to server for cross-browser sync
- Restore window states on reconnection/page reload
- New API: GET/PUT /api/subagent-window-states
- State file: ~/.claudeman/subagent-window-states.json

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

src/subagent-watcher.ts

@@ -242,6 +242,28 @@ export class SubagentWatcher extends EventEmitter {
     return this.agentInfo.get(agentId);
   }
 
+  /**
+   * Update a subagent's description.
+   * Used to set the short description from TaskTracker when available.
+   */
+  updateDescription(agentId: string, description: string): boolean {
+    const info = this.agentInfo.get(agentId);
+    if (info) {
+      info.description = description;
+      this.emit('subagent:updated', info);
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Find sessions whose working directory matches a project hash.
+   * Returns the project hash for a given working directory.
+   */
+  getProjectHashForDir(workingDir: string): string {
+    return this.getProjectHash(workingDir);
+  }
+
   /**
    * Get recent subagents (modified within specified minutes)
    */