* feat(web-shell): add token-usage analytics dashboard to Daemon Status
Add a "统计 / Usage" tab to the Daemon Status page: a Today/7D/30D period toggle over the selected range's token totals and input/output/cache-read breakdown, a 12-month token heatmap (per-day tokens + cache-read tooltip, localized month labels), per-model token share, skill-call counts, and daily token/session charts.
Backend: a new read-only GET /usage/dashboard daemon API backed by a core usage-dashboard service that aggregates the durable local usage history (cross-project ~/.qwen), reusing loadUsageHistory + aggregateUsage. Skill counts are threaded through the shared usage pipeline. No new instrumentation — every metric is read from data qwen-code already persists.
* fix(web-shell): address usage-dashboard review feedback
- cap `aggregateUsage` topSkills at 25 like topTools, so the aggregate and dashboard payload stay bounded
- fix a DST drift in the heatmap grid: advance the day/month cursor by calendar day (setDate) instead of a fixed `i * MS_PER_DAY` offset
- cache the loaded history once (range-independent) so toggling Today/7D/30D re-aggregates from a single disk read; split a pure `buildUsageDashboard(records, opts)` out of `loadUsageDashboard`
- drop the unused per-day streak computation and the dead `daemon.usage.streak` i18n key
- add debug logging to the dashboard builder and a direct `aggregateUsage`-skills unit test
* fix(usage-dashboard): make the dashboard load read-only + fix cache coalescing
- Make the daemon dashboard side-effect free: `loadUsageHistory` gains a `persistRebuild` option, and the route passes `persistRebuild: false`, so serving a GET never writes to `~/.qwen`. The transcript-rebuild fallback previously persisted rebuilt records (including an in-progress session), violating the read-only contract.
- Fix cache coalescing on the slow path: a pending history load is now reused regardless of age (the TTL starts at settlement), so a request arriving after the TTL while the load is still pending no longer kicks off a second full load.
- Tests: read-only rebuild writes nothing, `metricsToUsageRecord` copies `SessionMetrics.skills`, and a pending load is shared past the TTL.
