FN-6142: fix mobile visibility restore scroll anchoring

Restore pinned mobile chat scroll position when visibility-driven refetch hooks fire.

- re-anchor mobile chat to the bottom during visibility/pageshow refetch capture when the user was pinned
- tighten ChatView visibility restore regression tests to assert the synchronous re-anchor path directly
- remove the ChatView rooms test quarantine and restore the dashboard include list entry

Files changed:
 packages/dashboard/app/components/ChatView.tsx          |  6 +++++-
 .../app/components/__tests__/ChatView.rooms.test.tsx    | 17 ++++++++---------
 .../app/components/__tests__/ChatView.test.tsx          |  7 ++++---
 packages/dashboard/vitest.config.ts                     |  2 +-
 scripts/lib/test-quarantine.json                        |  8 +-------
 5 files changed, 19 insertions(+), 21 deletions(-)

Fusion-Task-Id: FN-6142

Fusion-Task-Lineage: 2974cf0d-5512-4b24-ab0c-2d2fb63fd41a

packages/dashboard/app/components/ChatView.tsx

@@ -1708,7 +1708,11 @@ export function ChatView({ projectId, addToast, experimentalFeatures }: ChatView
     }
 
     const captureForRefetch = () => {
+      const wasPinnedBefore = !isUserScrollingRef.current;
       captureScrollSnapshot();
+      if (wasPinnedBefore && isMobile && messagesContainerRef.current) {
+        scrollToBottom("visibility-restore");
+      }
     };
 
     const onVisibilityChange = () => {
@@ -1725,7 +1729,7 @@ export function ChatView({ projectId, addToast, experimentalFeatures }: ChatView
       document.removeEventListener("visibilitychange", onVisibilityChange);
       window.removeEventListener("pageshow", captureForRefetch);
     };
-  }, [isMobile, activeSession, roomThreadActive, captureScrollSnapshot]);
+  }, [isMobile, activeSession, roomThreadActive, captureScrollSnapshot, scrollToBottom]);
 
   useEffect(() => {
     if (roomThreadActive) {

packages/dashboard/app/components/__tests__/ChatView.rooms.test.tsx

@@ -801,9 +801,10 @@ describe("ChatView — rooms (FN-3805..FN-3811 contract)", () => {
       Object.defineProperty(document, "visibilityState", { configurable: true, value: "visible" });
       fireEvent(document, new Event("visibilitychange"));
 
-      await waitFor(() => {
-        expect(metrics.getScrollTop()).toBe(1180);
-      });
+      // Regression guard: visibility restore must explicitly re-anchor when pinned.
+      // This previously passed only when an old anchorToBottom rAF happened to run
+      // after the visibility event and masked that the handler only captured a snapshot.
+      expect(metrics.getScrollTop()).toBe(1180);
     } finally {
       metrics.restore();
       restoreMatchMedia.mockRestore();
@@ -826,9 +827,9 @@ describe("ChatView — rooms (FN-3805..FN-3811 contract)", () => {
       metrics.setScrollTop(300);
       fireEvent(window, new Event("pageshow"));
 
-      await waitFor(() => {
-        expect(metrics.getScrollTop()).toBe(1180);
-      });
+      // Regression guard: pageshow shares the visibility restore path and must not
+      // depend on leftover rAF callbacks from the initial mount anchor.
+      expect(metrics.getScrollTop()).toBe(1180);
     } finally {
       metrics.restore();
       restoreMatchMedia.mockRestore();
@@ -851,9 +852,7 @@ describe("ChatView — rooms (FN-3805..FN-3811 contract)", () => {
       Object.defineProperty(document, "visibilityState", { configurable: true, value: "visible" });
       fireEvent(document, new Event("visibilitychange"));
 
-      await waitFor(() => {
-        expect(metrics.getScrollTop()).toBe(300);
-      });
+      expect(metrics.getScrollTop()).toBe(300);
     } finally {
       metrics.restore();
       restoreMatchMedia.mockRestore();

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

@@ -4577,9 +4577,10 @@ describe("ChatView mobile behavior", () => {
       Object.defineProperty(document, "visibilityState", { configurable: true, value: "visible" });
       fireEvent(document, new Event("visibilitychange"));
 
-      await waitFor(() => {
-        expect(scrollTopValue).toBe(1180);
-      });
+      // Regression guard: visibility restore must explicitly re-anchor when pinned.
+      // Without that, this only passed when leftover anchorToBottom rAF callbacks
+      // happened to run after the visibility event.
+      expect(scrollTopValue).toBe(1180);
     } finally {
       restoreMatchMedia.mockRestore();
       Object.defineProperty(document, "visibilityState", { configurable: true, value: "visible" });

packages/dashboard/vitest.config.ts

@@ -231,7 +231,7 @@ const qualityAppComponentBatchBTests = buildComponentQualityInclude(batchedQuali
 const qualityAppAppOnlyTests = ["app/components/__tests__/App.test.tsx"];
 const qualityAppChatOnlyTests = ["app/components/__tests__/ChatView.test.tsx"];
 const qualityAppSettingsOnlyTests = ["app/components/__tests__/SettingsModal.test.tsx"];
-const quarantinedDashboardTests = ["app/components/__tests__/ChatView.rooms.test.tsx"];
+const quarantinedDashboardTests: string[] = [];
 
 const qualityApiTests = [
   // Critical HTTP/server behavior: auth, task/project/settings mutation,

scripts/lib/test-quarantine.json

@@ -1,10 +1,4 @@
 {
   "$comment": "Flaky-test quarantine ledger (deletion ratchet — see AGENTS.md 'Flaky tests: quarantine on sight' and docs/testing.md 'Quarantine ledger and the deletion ratchet'). A test observed failing without a corresponding real bug is quarantined ON SIGHT: add an entry here AND a matching one-line `exclude` entry in that package's vitest config, in the same commit. Every entry needs a non-empty `reason` (link the failing run) and a `quarantinedAt` date — the entry expires 14 days later, at which point the test file is DELETED unless someone rescues it with evidence it catches real regressions plus a root-cause fix (never appeasement). There is deliberately no loader module and no automation around this file: it is a dated record, the vitest config exclude is the mechanism, and the sweep is policy executed by whoever touches the suite.",
-  "entries": [
-    {
-      "file": "packages/dashboard/app/components/__tests__/ChatView.rooms.test.tsx",
-      "reason": "FN-6103 workspace pnpm test observed flaky mobile visibility restore assertion: expected scrollTop 1180, received 300 in ChatView.rooms.test.tsx:805; unrelated to CSS-only composer button sizing change.",
-      "quarantinedAt": "2026-06-09"
-    }
-  ]
+  "entries": []
 }