feat(FN-991): add per-task planning model override for triage and dashboard

- Add planningModelProvider/planningModelId fields to task model and API batch-update endpoint
- Wire triage engine to use per-task planning model override with settings hierarchy fallback
- Add planning model selector to TaskDetailModal Model tab
- Add comprehensive tests for triage engine planning model resolution and dashboard API/routes

packages/dashboard/app/components/TaskDetailModal.tsx

@@ -102,21 +102,30 @@ function extractPlanningModelFromLog(entries: AgentLogEntry[]): { provider: stri
 
 /**
  * Resolve the effective planning/triage model following the resolution order:
- * 1. Runtime triage model from agent log marker (if present)
- * 2. Project settings planningProvider/planningModelId
- * 3. Global settings defaultProvider/defaultModelId
+ * 1. Per-task planningModelProvider/planningModelId override
+ * 2. Runtime triage model from agent log marker (if present)
+ * 3. Project settings planningProvider/planningModelId
+ * 4. Global settings defaultProvider/defaultModelId
  */
 function resolveEffectivePlanning(
+  task: Task | TaskDetail,
   logEntries: AgentLogEntry[],
   settings?: Settings,
 ): ModelSelection {
+  // 1. Per-task override takes precedence
+  if (task.planningModelProvider && task.planningModelId) {
+    return { provider: task.planningModelProvider, modelId: task.planningModelId };
+  }
+  // 2. Runtime triage model from agent log marker
   const fromLog = extractPlanningModelFromLog(logEntries);
   if (fromLog) {
     return fromLog;
   }
+  // 3. Project settings planningProvider/planningModelId
   if (settings?.planningProvider && settings.planningModelId) {
     return { provider: settings.planningProvider, modelId: settings.planningModelId };
   }
+  // 4. Global settings defaultProvider/defaultModelId
   if (settings?.defaultProvider && settings.defaultModelId) {
     return { provider: settings.defaultProvider, modelId: settings.defaultModelId };
   }
@@ -922,7 +931,7 @@ export function TaskDetailModal({
                   loading={agentLogLoading}
                   executorModel={resolveEffectiveExecutor(task, settings)}
                   validatorModel={resolveEffectiveValidator(task, settings)}
-                  planningModel={resolveEffectivePlanning(agentLogEntries, settings)}
+                  planningModel={resolveEffectivePlanning(task, agentLogEntries, settings)}
                 />
               ) : (
                 <div className="detail-activity">

packages/dashboard/app/components/__tests__/TaskDetailModal.test.tsx

@@ -1439,6 +1439,59 @@ describe("TaskDetailModal", () => {
         expect(defaultBadges).toHaveLength(3);
       });
 
+      it("per-task planning model override takes precedence over settings", async () => {
+        const { fetchSettings } = await import("../../api");
+        const { useAgentLogs } = await import("../../hooks/useAgentLogs");
+
+        vi.mocked(fetchSettings).mockResolvedValueOnce({
+          modelPresets: [],
+          autoSelectModelPreset: false,
+          defaultPresetBySize: {},
+          defaultProvider: "anthropic",
+          defaultModelId: "claude-sonnet-4-5",
+          planningProvider: "openai",
+          planningModelId: "gpt-4o",
+        } as any);
+
+        vi.mocked(useAgentLogs).mockReturnValue({
+          entries: [mockLogEntry],
+          loading: false,
+          clear: vi.fn(),
+        });
+
+        const { container } = render(
+          <TaskDetailModal
+            task={makeTask({
+              prompt: "# Hello\n\nContent",
+              planningModelProvider: "google",
+              planningModelId: "gemini-2.5-pro",
+            })}
+            onClose={noop}
+            onMoveTask={noopMove}
+            onDeleteTask={noopDelete}
+            onMergeTask={noopMerge}
+            onOpenDetail={noopOpenDetail}
+            addToast={noop}
+          />,
+        );
+
+        // Navigate to Agent Log subview
+        fireEvent.click(screen.getByText("Logs"));
+        fireEvent.click(screen.getByText("Agent Log"));
+
+        await waitFor(() => {
+          const header = container.querySelector("[data-testid='agent-log-model-header']");
+          expect(header).toBeTruthy();
+          // Per-task override should take precedence over settings
+          expect(header!.textContent).toContain("Planning/Triage:");
+          expect(header!.textContent).toContain("google/gemini-2.5-pro");
+        });
+
+        const header = container.querySelector("[data-testid='agent-log-model-header']")!;
+        // Should NOT show the settings planning model
+        expect(header.textContent).not.toContain("openai/gpt-4o");
+      });
+
       it("runtime triage marker takes precedence over planningProvider settings", async () => {
         const { fetchSettings } = await import("../../api");
         const { useAgentLogs } = await import("../../hooks/useAgentLogs");