fix(workouts): read a day with activity data and no workout as rest

The strain run writes no impulse row on a day without a scorable workout
or active energy, so a rest day for someone without daily active energy
was never rated: fitness and fatigue held for months instead of
decaying, and the figures named the last stored day while the coverage
count ended there too.

A day without a stored impulse is now classified from the underlying
data: a workout on the day leaves it unrated, steps, heart rate or
active energy without a workout make it rest, and no data at all leaves
it unrated. The series runs to the day the strain run scores, so a
stretch without data after the last rated day shows in the coverage
count, and the card names the last rated day when it lies further back
than the day before.

src/app/api/workouts/__tests__/canonical-dedup.test.ts

@@ -28,6 +28,8 @@ vi.mock("@/lib/db", () => ({
     },
     // v1.44 — the first page carries the training load.
     strainTrimpCache: { findMany: vi.fn(async () => []) },
+    measurementRollup: { findMany: vi.fn(async () => []) },
+    $queryRaw: vi.fn(async () => []),
   },
 }));