Add boundary carry-in tests for /activity/stats and /activity/daily-status

[selfcontained]

Summary

Recurring test-enforcer maintenance run. Local suite was green at start (check ✓, unit 2281+232+51 ✓, E2E 168 pass/13 skip ✓), so this run closes the highest-value coverage gap identified by the prior run's next_focus.

handleStats and handleDailyStatus both route through loadScopedActivityEvents (apps/server/src/server/activity-query.ts), which merges an in-range query with a DISTINCT ON (agent_id) … WHERE created_at < rangeStart ORDER BY created_at DESC boundary query to carry in each agent's latest pre-range event, then clamps its duration to the range start. That carry-in logic had boundary coverage for working-time-by-project (#787) but zero coverage for these two other consumers.

Tests added (4)

• stats — clamps a pre-range working session to the range start (30 min counted, not the 150 before it)
• stats — carries in the latest pre-range event, not the earliest (a pre-range done accrues 0)
• daily-status — same clamp, asserted by summing working duration across buckets
• daily-status — a completed pre-range session accrues no time

daily-status assertions sum working duration across day buckets rather than asserting bucket keys, because computeDailyStatus buckets by server-local date — the summed clamped total is timezone-independent, avoiding CI flakiness.

Validation

• pnpm run check ✓
• pnpm run test ✓ — server 2285 pass (was 2281, +4), web 232, browser-ext 51, all green
• pnpm run test:e2e ✓ (baseline) — 168 pass / 13 skip; no product code changed so E2E is unaffected
• One general review agent traced all four assertions through the merge + compute logic: correct, no timezone/ordering/cleanup flakiness, no changes recommended.

Test-only change.

🤖 Generated with Claude Code