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/web/src/components/review/ReviewHeader.tsx

@@ -46,6 +46,7 @@ interface ReviewHeaderProps {
   unresolvedCount: number;
   onApprove: () => void;
   onRequestChanges: () => void;
+  isRequestingChanges?: boolean;
   preview: PreviewState | null;
   viewedCount?: number;
   totalCount?: number;
@@ -63,6 +64,7 @@ export function ReviewHeader({
   unresolvedCount,
   onApprove,
   onRequestChanges,
+  isRequestingChanges,
   preview,
   viewedCount,
   totalCount,
@@ -186,9 +188,14 @@ export function ReviewHeader({
                 variant="outline"
                 size="sm"
                 onClick={onRequestChanges}
+                disabled={isRequestingChanges}
                 className="h-8 text-xs px-3 border-status-error-border/50 text-status-error-fg hover:bg-status-error-bg/50 hover:border-status-error-border"
               >
-                <X className="h-3 w-3" />
+                {isRequestingChanges ? (
+                  <Loader2 className="h-3 w-3 animate-spin" />
+                ) : (
+                  <X className="h-3 w-3" />
+                )}
                 Request Changes
               </Button>
               <div className="relative" ref={confirmRef}>

apps/web/src/components/review/ReviewTab.tsx

@@ -225,12 +225,21 @@ export function ReviewTab({ initiativeId }: ReviewTabProps) {
     approveMutation.mutate({ phaseId: activePhaseId });
   }, [activePhaseId, approveMutation]);
 
+  const requestChangesMutation = trpc.requestPhaseChanges.useMutation({
+    onSuccess: () => {
+      setStatus("changes_requested");
+      toast.success("Changes requested — revision task dispatched");
+      phasesQuery.refetch();
+    },
+    onError: (err) => toast.error(err.message),
+  });
+
   const handleRequestChanges = useCallback(() => {
-    setStatus("changes_requested");
-    toast("Changes requested", {
-      description: "The agent will be notified about the requested changes.",
-    });
-  }, []);
+    if (!activePhaseId) return;
+    const summary = window.prompt("Optional: describe what needs to change (leave blank for comments only)");
+    if (summary === null) return; // cancelled
+    requestChangesMutation.mutate({ phaseId: activePhaseId, summary: summary || undefined });
+  }, [activePhaseId, requestChangesMutation]);
 
   const handleFileClick = useCallback((filePath: string) => {
     const el = fileRefs.current.get(filePath);
@@ -282,6 +291,7 @@ export function ReviewTab({ initiativeId }: ReviewTabProps) {
         unresolvedCount={unresolvedCount}
         onApprove={handleApprove}
         onRequestChanges={handleRequestChanges}
+        isRequestingChanges={requestChangesMutation.isPending}
         preview={previewState}
         viewedCount={viewedFiles.size}
         totalCount={allFiles.length}