feat(P2+P3): IHF Phase 2 complete; register Phase 3 workplan

Phase 2 — Structured Feedback and Triage (IHUB-WP-0002):
- Schema: annotation_threads, requirement_candidates, triage_states,
  reviewer_assignments; annotations extended with severity + thread_id
- AnnotationThreadsController: create threads, assign annotations
- RequirementCandidatesController: CRUD, escalation, triage lifecycle,
  reviewer assignment, my-queue
- Annotation severity (low/medium/high/critical) with Tailwind color cues
- TriageDashboardAction on HubsController with autoRefresh
- Integration tests (T01–T09), SCOPE.md updated, docs/phase2-summary.md

Phase 3 — Governance and Decision Linkage (IHUB-WP-0003):
- Workplan registered: 9 tasks, State Hub workstream 5f201ee3

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Web/Controller/AnnotationThreads.hs

@@ -0,0 +1,65 @@
+module Web.Controller.AnnotationThreads where
+
+import Web.Types
+import Web.View.AnnotationThreads.Index
+import Web.View.AnnotationThreads.New
+import Web.View.AnnotationThreads.Show
+import Generated.Types
+import IHP.Prelude
+import IHP.ControllerPrelude
+
+instance Controller AnnotationThreadsController where
+    beforeAction = ensureIsUser
+
+    action WidgetAnnotationThreadsAction { widgetId } = do
+        widget  <- fetch widgetId
+        threads <- query @AnnotationThread
+            |> filterWhere (#widgetId, widgetId)
+            |> orderByDesc #createdAt
+            |> fetch
+        -- Fetch annotation counts per thread
+        allAnnotations <- query @Annotation
+            |> filterWhere (#widgetId, widgetId)
+            |> fetch
+        render IndexView { widget, threads, allAnnotations }
+
+    action ShowAnnotationThreadAction { annotationThreadId } = do
+        thread      <- fetch annotationThreadId
+        widget      <- fetch thread.widgetId
+        annotations <- query @Annotation
+            |> filterWhere (#threadId, Just annotationThreadId)
+            |> orderByAsc #createdAt
+            |> fetch
+        render ShowView { widget, thread, annotations }
+
+    action NewAnnotationThreadAction { widgetId } = do
+        widget <- fetch widgetId
+        let thread = newRecord @AnnotationThread
+        render NewView { widget, thread }
+
+    action CreateAnnotationThreadAction { widgetId } = do
+        widget <- fetch widgetId
+        mUser  <- currentUserOrNothing
+        let createdBy = fmap (.id) mUser
+
+        let thread = newRecord @AnnotationThread
+        thread
+            |> fill @'["title", "description"]
+            |> set #widgetId widgetId
+            |> set #createdBy (fmap (Id . unId) createdBy)
+            |> validateField #title nonEmpty
+            |> ifValid \case
+                Left thread  -> render NewView { widget, thread }
+                Right thread -> do
+                    createRecord thread
+                    setSuccessMessage "Thread created"
+                    redirectTo WidgetAnnotationThreadsAction { widgetId }
+
+    action AssignAnnotationToThreadAction { annotationId } = do
+        annotation <- fetch annotationId
+        threadId   <- param @(Id AnnotationThread) "threadId"
+        annotation
+            |> set #threadId (Just threadId)
+            |> updateRecord
+        setSuccessMessage "Annotation added to thread"
+        redirectTo ShowAnnotationThreadAction { annotationThreadId = threadId }