fix: subagent title extraction race condition

- Add 100ms debounce for new file detection to allow content to be written
- Add subagent:updated event for retroactive description updates
- Extract description in processEntry when first user message is processed
- Add extractDescriptionFromFile helper with retry in file change handler
- Update SubagentTranscriptEntry.content type to support string | array
- Add test coverage for subagent:updated event

Fixes 43% failure rate where subagents displayed raw IDs instead of descriptions
due to race condition when files were discovered before first line was written.

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

src/web/public/app.js

@@ -1308,6 +1308,23 @@ class ClaudemanApp {
       }
     });
 
+    this.eventSource.addEventListener('subagent:updated', (e) => {
+      const data = JSON.parse(e.data);
+      const existing = this.subagents.get(data.agentId);
+      if (existing) {
+        // Merge updated fields (especially description)
+        Object.assign(existing, data);
+        this.subagents.set(data.agentId, existing);
+      } else {
+        this.subagents.set(data.agentId, data);
+      }
+      this.renderSubagentPanel();
+      // Update floating window if open
+      if (this.subagentWindows.has(data.agentId)) {
+        this.renderSubagentWindowContent(data.agentId);
+      }
+    });
+
     this.eventSource.addEventListener('subagent:tool_call', (e) => {
       const data = JSON.parse(e.data);
       const activity = this.subagentActivity.get(data.agentId) || [];

src/web/server.ts

@@ -303,6 +303,10 @@ export class WebServer extends EventEmitter {
       this.broadcast('subagent:discovered', info);
     });
 
+    subagentWatcher.on('subagent:updated', (info: SubagentInfo) => {
+      this.broadcast('subagent:updated', info);
+    });
+
     subagentWatcher.on('subagent:tool_call', (data: SubagentToolCall) => {
       this.broadcast('subagent:tool_call', data);
     });