v0.3.5

Added

• Usage History tab. A new dashboard tab surfaces long-run usage trends
  sampled from /v1/usage. Built across seven tickets (01–07):
  • Ticket 01: coalesced /v1/usage history fetch with a ring-buffer
    sample store (usage_samples), gated by usage_history_enabled.
  • Ticket 02: usage_events table + priority/service-mode tuple
    detector with a GET /dashboard/api/usage/events endpoint for
    transition logging.
  • Ticket 03: usage_daily downsampled rows with gap detection and
    self-healing across retention boundaries (days older than
    usage_raw_retention_days are pruned after a daily row is written).
  • Ticket 04: dual-channel calendar heatmap (activity density + cache
    hit rate) with brush-to-zoom day selection.
  • Ticket 05: 5-lane timeline drill-down (concurrency, requests,
    token flow, cache hit rate, degradation state) with ban-onset vertical
    lines spanning all lanes.
  • Ticket 06: old-day timeline rendered from usage_daily +
    usage_events using a hybrid step-function with dashed held-constant
    segments and accurate degradation bands.
  • Ticket 07: WebSocket live updates (usage-sample, usage-event),
    config hot-reload for the three usage-history knobs, and a CONTEXT.md
    glossary.
• Config tab: Usage History section exposing usage_history_enabled,
  usage_raw_retention_days, and usage_gap_threshold_minutes — all
  hot-reloadable.

Fixed

• Stamp: restamp cache_control breakpoints to Layout B. The stamp
  pipeline now reorders cache_control breakpoints to the canonical
  Layout B ordering before stamping, so restamped requests are stable
  across re-sends.
• Usage history: self-healing data loss across retention boundaries.
  runDailyDownsample previously downsampled from today-retention to
  today, which left days older than the retention cutoff without a
  daily row before pruning their raw samples — silent data loss when the
  proxy was down across a retention boundary. Fixed by using
  getEarliestSampleDay() as the from date so every day with samples
  gets its daily row written before pruning.
• Config validation: restored models_refresh_ms to integer
  validation. A duplicate usage_refresh_ms entry in INT_FIELDS
  (introduced in ticket 03) had silently replaced models_refresh_ms,
  removing its integer validation. Removed the duplicate and restored
  models_refresh_ms.