feat(FN-4608): complete Step 2 — handle empty-sample reliability days

Fusion-Task-Id: FN-4608
Fusion-Task-Lineage: 6cabc509-38a1-4cb8-be6f-51c53d5753ff

packages/dashboard/src/__tests__/reliability-metrics.test.ts

@@ -4,6 +4,7 @@ import type { ActivityLogEntry, RunAuditEvent } from "@fusion/core";
 
 import {
   bucketByDay,
+  dayHasSamples,
   fileScopeInvariantFailuresPerDay,
   inReviewDurationMetrics,
   inReviewFailureRate7d,
@@ -136,4 +137,52 @@ describe("reliability-metrics", () => {
     expect(inReviewFailureRate7d({ "2026-05-13": 10 }, { "2026-05-13": 2 }, endMs)).toEqual({ value: 0.2 });
     expect(inReviewFailureRate7d({}, {}, endMs)).toEqual({ value: null, reason: "no-in-review-entries" });
   });
+
+  it("returns no-in-review-entries when all seven days are empty", () => {
+    const endMs = Date.parse("2026-05-13T00:00:00.000Z");
+    expect(inReviewFailureRate7d({ "2026-05-13": 0, "2026-05-12": 0 }, { "2026-05-13": 0 }, endMs)).toEqual({
+      value: null,
+      reason: "no-in-review-entries",
+    });
+  });
+
+  it("filters task movement counts by start/end window", () => {
+    const activity: ActivityLogEntry[] = [
+      moved("2026-05-10T23:59:59.000Z", "FN-1", "todo", "in-review"),
+      moved("2026-05-11T00:00:00.000Z", "FN-2", "todo", "in-review"),
+      moved("2026-05-12T00:00:00.000Z", "FN-3", "in-review", "in-progress"),
+    ];
+
+    const start = Date.parse("2026-05-11T00:00:00.000Z");
+    const end = Date.parse("2026-05-12T00:00:00.000Z");
+
+    expect(tasksEnteredInReviewPerDay(activity, start, end)).toEqual({ "2026-05-11": 1 });
+    expect(tasksBouncedToInProgressPerDay(activity, start, end)).toEqual({ "2026-05-12": 1 });
+  });
+
+  it("reports hasSamples semantics for per-day rows", () => {
+    expect(dayHasSamples({
+      tasksEnteredInReview: 0,
+      tasksBouncedToInProgress: 0,
+      postMergeAuditFailures: null,
+      fileScopeInvariantFailures: null,
+      recoverAlreadyMergedReviewTasksRecoveries: null,
+    })).toBe(false);
+
+    expect(dayHasSamples({
+      tasksEnteredInReview: 0,
+      tasksBouncedToInProgress: 1,
+      postMergeAuditFailures: null,
+      fileScopeInvariantFailures: null,
+      recoverAlreadyMergedReviewTasksRecoveries: null,
+    })).toBe(true);
+
+    expect(dayHasSamples({
+      tasksEnteredInReview: 0,
+      tasksBouncedToInProgress: 0,
+      postMergeAuditFailures: { block: 0, warn: 1, off: 0 },
+      fileScopeInvariantFailures: 0,
+      recoverAlreadyMergedReviewTasksRecoveries: 0,
+    })).toBe(true);
+  });
 });

packages/dashboard/src/reliability-metrics.ts

@@ -29,6 +29,14 @@ export interface InReviewDurationMetric {
   reason?: NullMetricReason;
 }
 
+export interface ReliabilityPerDayCounts {
+  tasksEnteredInReview: number;
+  tasksBouncedToInProgress: number;
+  postMergeAuditFailures: { block: number; warn: number; off: number } | null;
+  fileScopeInvariantFailures: number | null;
+  recoverAlreadyMergedReviewTasksRecoveries: number | null;
+}
+
 const DAY_MS = 86_400_000;
 
 export function bucketByDay(timestamp: string): string {
@@ -183,6 +191,21 @@ export function mergeAttemptsPerMergedTask(events: RunAuditEvent[], activity: Ac
   };
 }
 
+export function dayHasSamples(counts: ReliabilityPerDayCounts): boolean {
+  if (counts.tasksEnteredInReview > 0 || counts.tasksBouncedToInProgress > 0) {
+    return true;
+  }
+
+  if (counts.postMergeAuditFailures) {
+    const { block, warn, off } = counts.postMergeAuditFailures;
+    if (block + warn + off > 0) {
+      return true;
+    }
+  }
+
+  return (counts.fileScopeInvariantFailures ?? 0) > 0 || (counts.recoverAlreadyMergedReviewTasksRecoveries ?? 0) > 0;
+}
+
 export function inReviewFailureRate7d(enteredByDay: Record<string, number>, bouncedByDay: Record<string, number>, endMs: number): NullableMetric<number> {
   let entered = 0;
   let bounced = 0;

packages/dashboard/src/server.ts

@@ -61,6 +61,7 @@ import { createAuthMiddleware, authenticateUpgradeRequest, getDaemonToken } from
 import { validateRemoteAuthToken } from "./remote-auth.js";
 import { getCliPackageVersion } from "./cli-package-version.js";
 import {
+  dayHasSamples,
   fileScopeInvariantFailuresPerDay,
   inReviewDurationMetrics,
   inReviewFailureRate7d,
@@ -1167,11 +1168,13 @@ export function createServer(store: TaskStore, options?: ServerOptions): ReturnT
       const postMergeAuditFailures = postMergeByDay.value ? (postMergeByDay.value[day] ?? { block: 0, warn: 0, off: 0 }) : null;
       const fileScopeInvariantFailures = fileScopeByDay.value ? (fileScopeByDay.value[day] ?? 0) : null;
       const recoverAlreadyMergedReviewTasksRecoveries = recoveriesByDay.value ? (recoveriesByDay.value[day] ?? 0) : null;
-      const hasSamples = tasksEnteredInReview > 0
-        || tasksBouncedToInProgress > 0
-        || (postMergeAuditFailures ? postMergeAuditFailures.block + postMergeAuditFailures.warn + postMergeAuditFailures.off > 0 : false)
-        || (typeof fileScopeInvariantFailures === "number" && fileScopeInvariantFailures > 0)
-        || (typeof recoverAlreadyMergedReviewTasksRecoveries === "number" && recoverAlreadyMergedReviewTasksRecoveries > 0);
+      const hasSamples = dayHasSamples({
+        tasksEnteredInReview,
+        tasksBouncedToInProgress,
+        postMergeAuditFailures,
+        fileScopeInvariantFailures,
+        recoverAlreadyMergedReviewTasksRecoveries,
+      });
 
       perDay.push({
         date: day,