feat(FN-4288): complete Step 1 — add in-review stall copy module

Fusion-Task-Id: FN-4288
Fusion-Task-Lineage: 09c6efc0-ea0b-443a-ab45-a89188fcf888

packages/dashboard/app/utils/__tests__/inReviewStallCopy.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, it } from "vitest";
+
+import { getInReviewStallCopy, shouldShowInReviewStallBadge } from "../inReviewStallCopy";
+
+describe("inReviewStallCopy", () => {
+  it.each([
+    "merge-blocker",
+    "transient-merge-status-no-owner",
+    "merge-retries-exhausted",
+    "no-worktree-no-merge-confirmed",
+  ] as const)("returns populated copy for %s", (code) => {
+    const copy = getInReviewStallCopy({
+      code,
+      reason: "reason",
+      observedAt: "2026-05-13T00:00:00.000Z",
+    });
+
+    expect(copy.badgeLabel).toBe("Stall");
+    expect(copy.headline.length).toBeGreaterThan(0);
+    expect(copy.description.length).toBeGreaterThan(0);
+    expect(copy.suggestedAction.length).toBeGreaterThan(0);
+  });
+
+  it.each([
+    { column: "in-review", paused: false, inReviewStall: undefined },
+    {
+      column: "in-review",
+      paused: true,
+      inReviewStall: { code: "merge-blocker", reason: "r", observedAt: "2026-05-13T00:00:00.000Z" },
+    },
+    {
+      column: "in-progress",
+      paused: false,
+      inReviewStall: { code: "merge-blocker", reason: "r", observedAt: "2026-05-13T00:00:00.000Z" },
+    },
+  ] as const)("hides badge for non-canonical visibility cases", (task) => {
+    expect(shouldShowInReviewStallBadge(task)).toBe(false);
+  });
+
+  it("shows badge only for in-review non-paused task with signal", () => {
+    expect(
+      shouldShowInReviewStallBadge({
+        column: "in-review",
+        paused: false,
+        inReviewStall: { code: "merge-blocker", reason: "r", observedAt: "2026-05-13T00:00:00.000Z" },
+      }),
+    ).toBe(true);
+  });
+
+  it("falls back to defensive default for unknown codes", () => {
+    const copy = getInReviewStallCopy({
+      code: "future-code" as never,
+      reason: "future reason",
+      observedAt: "2026-05-13T00:00:00.000Z",
+    });
+
+    expect(copy.headline).toBe("In-review stall surfaced");
+    expect(copy.description).toBe("future reason");
+    expect(copy.suggestedAction).toBe("Open the activity log for details.");
+    expect(copy.badgeLabel).toBe("Stall");
+  });
+});