feat: Wire full request-changes flow for phase review

- Add PhaseChangesRequestedEvent to event bus
- Add requestChangesOnPhase() to ExecutionOrchestrator: reads unresolved
  comments, creates revision task (category='review'), resets phase to
  in_progress, queues task for dispatch
- Expand merge-skip and branch routing to include 'review' category so
  revision tasks work directly on the phase branch
- Add requestPhaseChanges tRPC procedure (reads comments from DB)
- Wire frontend: mutation replaces stub handler, window.prompt for
  optional summary, loading state on button

apps/server/trpc/routers/phase.ts

@@ -341,5 +341,38 @@ export function phaseProcedures(publicProcedure: ProcedureBuilder) {
         }
         return comment;
       }),
+
+    requestPhaseChanges: publicProcedure
+      .input(z.object({
+        phaseId: z.string().min(1),
+        summary: z.string().optional(),
+      }))
+      .mutation(async ({ ctx, input }) => {
+        const orchestrator = requireExecutionOrchestrator(ctx);
+        const reviewCommentRepo = requireReviewCommentRepository(ctx);
+
+        const allComments = await reviewCommentRepo.findByPhaseId(input.phaseId);
+        const unresolved = allComments
+          .filter((c: { resolved: boolean }) => !c.resolved)
+          .map((c: { filePath: string; lineNumber: number; body: string }) => ({
+            filePath: c.filePath,
+            lineNumber: c.lineNumber,
+            body: c.body,
+          }));
+
+        if (unresolved.length === 0 && !input.summary) {
+          throw new TRPCError({
+            code: 'BAD_REQUEST',
+            message: 'Add comments or a summary before requesting changes',
+          });
+        }
+
+        const result = await orchestrator.requestChangesOnPhase(
+          input.phaseId,
+          unresolved,
+          input.summary,
+        );
+        return { success: true, taskId: result.taskId };
+      }),
   };
 }