Address PR review feedback (#1694)

- TaskChatTab: add FNXC:TaskDetailChat prefix/date to the ephemeral
  active-session comment, matching the file's comment convention.
- useModalManager: clear stale planning/subtask resume-session id (and
  initial plan) when opening a fresh planning/subtask flow, so the modal
  no longer reopens into a prior session.
- boardWorkflowsCache: validate cached workflow item shape (id/name/
  columns) and taskWorkflowIds value types so a malformed cache entry
  can't pass and later crash Board on render.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/TaskChatTab.tsx

@@ -177,6 +177,7 @@ function isActiveAgentSession(task: Task | TaskDetail, opts: { sessionLive?: boo
   const statusAllowsReviewSteering = !task.status || REVIEW_STEERABLE_STATUSES.has(task.status);
   const columnAllowsSteering = (task.column === "in-progress" && statusAllowsProgressSteering)
     || (task.column === "in-review" && statusAllowsReviewSteering);
+  // FNXC:TaskDetailChat 2026-06-20-20:10:
   // In the default ephemeral-agents mode the scheduler never writes
   // `assignedAgentId`/`checkedOutBy` — those are only set when
   // `ephemeralAgentsEnabled === false` (scheduler.ts). An actively-executing

packages/dashboard/app/hooks/useModalManager.ts

@@ -234,10 +234,19 @@ export function useModalManager(options: UseModalManagerOptions): ModalManager {
   }, []);
 
   const openPlanning = useCallback(() => {
+    // FNXC:PlanningModals 2026-06-20-20:10:
+    // A fresh planning open must clear any resume-session id / initial plan left
+    // by a prior resumePlanning/openPlanningWith* flow; otherwise the modal reopens
+    // into the stale session or pre-fills an old plan instead of starting blank.
+    setPlanningResumeSessionId(undefined);
+    setPlanningInitialPlan(null);
     setPlanningWorkflowId(undefined);
     setIsPlanningOpen(true);
   }, []);
   const openPlanningWithInitialPlan = useCallback((initialPlan: string, workflowId?: string | null) => {
+    // FNXC:PlanningModals 2026-06-20-20:10: clear a stale resume-session id so the
+    // supplied initial plan is honored rather than being overridden by an old session.
+    setPlanningResumeSessionId(undefined);
     setPlanningInitialPlan(initialPlan);
     setPlanningWorkflowId(workflowId);
     setIsPlanningOpen(true);
@@ -262,6 +271,9 @@ export function useModalManager(options: UseModalManagerOptions): ModalManager {
   }, []);
 
   const openSubtaskBreakdown = useCallback((description: string, workflowId?: string | null) => {
+    // FNXC:PlanningModals 2026-06-20-20:10: clear a stale subtask resume-session id
+    // so a new breakdown starts fresh rather than reopening a prior session.
+    setSubtaskResumeSessionId(undefined);
     setSubtaskInitialDescription(description);
     setSubtaskWorkflowId(workflowId);
     setIsSubtaskOpen(true);

packages/dashboard/app/utils/boardWorkflowsCache.ts

@@ -1,4 +1,4 @@
-import type { BoardWorkflowsPayload } from "../api";
+import type { BoardWorkflowDefinition, BoardWorkflowsPayload } from "../api";
 
 const BOARD_WORKFLOWS_CACHE_PREFIX = "fusion:board-workflows:";
 const DEFAULT_PROJECT_CACHE_KEY = "default";
@@ -17,6 +17,20 @@ function isBoardWorkflowsPayload(value: unknown): value is BoardWorkflowsPayload
   if (!Array.isArray(value.workflows)) return false;
   if (typeof value.defaultWorkflowId !== "string") return false;
   if (!isRecord(value.taskWorkflowIds)) return false;
+  // FNXC:BoardWorkflows 2026-06-20-20:10:
+  // Validate each cached workflow's shape and the taskWorkflowIds value types,
+  // not just the container types. A malformed entry (e.g. `[{}]` from a stale or
+  // partially-written cache) would otherwise pass and later throw in Board/ListView
+  // when accessing workflow.name/columns — re-introducing the legacy flash this
+  // cache exists to prevent. Mirrors the BoardWorkflowDefinition contract (id, name,
+  // columns) and the Record<string,string> taskWorkflowIds map.
+  if (!value.workflows.every((workflow): workflow is BoardWorkflowDefinition => (
+    isRecord(workflow)
+    && typeof workflow.id === "string"
+    && typeof workflow.name === "string"
+    && Array.isArray(workflow.columns)
+  ))) return false;
+  if (!Object.values(value.taskWorkflowIds).every((workflowId) => typeof workflowId === "string")) return false;
   return true;
 }