feat: Add threaded review comments + agent comment responses

Introduces GitHub-style threaded comments via parentCommentId self-reference.
Users and agents can reply within comment threads, and review agents receive
comment IDs so they can post targeted responses via comment-responses.json.

- Migration 0032: parentCommentId column + index on review_comments
- Repository: createReply() copies parent context, default author 'you' → 'user'
- tRPC: replyToReviewComment procedure, requestPhaseChanges passes threaded comments
- Orchestrator: formats [comment:ID] tags with full reply threads in task description
- Agent IO: readCommentResponses() reads .cw/output/comment-responses.json
- OutputHandler: processes agent comment responses (creates replies, resolves threads)
- Execute prompt: conditional <review_comments> block when task has [comment:] markers
- Frontend: CommentThread renders root+replies with agent-specific styling + reply form
- Sidebar/ReviewTab: root-only comment counts, reply mutation plumbing through DiffViewer chain

apps/server/execution/orchestrator.ts

@@ -344,7 +344,14 @@ export class ExecutionOrchestrator {
    */
   async requestChangesOnPhase(
     phaseId: string,
-    unresolvedComments: Array<{ filePath: string; lineNumber: number; body: string }>,
+    unresolvedThreads: Array<{
+      id: string;
+      filePath: string;
+      lineNumber: number;
+      body: string;
+      author: string;
+      replies: Array<{ id: string; body: string; author: string }>;
+    }>,
     summary?: string,
   ): Promise<{ taskId: string }> {
     const phase = await this.phaseRepository.findById(phaseId);
@@ -365,16 +372,16 @@ export class ExecutionOrchestrator {
       return { taskId: activeReview.id };
     }
 
-    // Build revision task description from comments + summary
+    // Build revision task description from threaded comments + summary
     const lines: string[] = [];
     if (summary) {
       lines.push(`## Summary\n\n${summary}\n`);
     }
-    if (unresolvedComments.length > 0) {
+    if (unresolvedThreads.length > 0) {
       lines.push('## Review Comments\n');
       // Group comments by file
-      const byFile = new Map<string, typeof unresolvedComments>();
-      for (const c of unresolvedComments) {
+      const byFile = new Map<string, typeof unresolvedThreads>();
+      for (const c of unresolvedThreads) {
         const arr = byFile.get(c.filePath) ?? [];
         arr.push(c);
         byFile.set(c.filePath, arr);
@@ -382,9 +389,13 @@ export class ExecutionOrchestrator {
       for (const [filePath, fileComments] of byFile) {
         lines.push(`### ${filePath}\n`);
         for (const c of fileComments) {
-          lines.push(`- **Line ${c.lineNumber}**: ${c.body}`);
+          lines.push(`#### Line ${c.lineNumber} [comment:${c.id}]`);
+          lines.push(`**${c.author}**: ${c.body}`);
+          for (const r of c.replies) {
+            lines.push(`> **${r.author}**: ${r.body}`);
+          }
+          lines.push('');
         }
-        lines.push('');
       }
     }
 
@@ -414,12 +425,12 @@ export class ExecutionOrchestrator {
         phaseId,
         initiativeId: phase.initiativeId,
         taskId: task.id,
-        commentCount: unresolvedComments.length,
+        commentCount: unresolvedThreads.length,
       },
     };
     this.eventBus.emit(event);
 
-    log.info({ phaseId, taskId: task.id, commentCount: unresolvedComments.length }, 'changes requested on phase');
+    log.info({ phaseId, taskId: task.id, commentCount: unresolvedThreads.length }, 'changes requested on phase');
 
     // Kick off dispatch
     this.scheduleDispatch();