v0.5.0

Changed

• Smart TTFT watchdog with dynamic two-tier threshold: replaced the
  static 60-second TTFT watchdog (ttft_timeout_ms) with a dynamic
  two-tier threshold derived from the upstream's real-time p50 latency
  via /v1/status. Attempt 1 starts at a fallback
  min(ttft_timeout_ms, upstream_timeout_ms-1000) and tightens to
  min(modelP50×multiplier, effective_hard_cap) when the status
  response arrives mid-flight. Attempts 2+ use
  effective_hard_cap = min(ttft_watchdog_hard_cap_ms, upstream_timeout_ms-1000).
  Attempt 3 rewrite-escalation is now unconditional (decoupled from
  experiment_rewrite_ids). After 3 failed attempts the proxy returns
  504. TtftWatchdogState (auto-disable) is removed entirely. A single
  ttft_timeout incident is recorded at capture lifecycle end instead
  of per-timeout. The dashboard badge unifies retry/cooldown/watching
  states with threshold display, and a new capture-card row 4 shows
  p50/tps/ratio when upstream p50 data is available.

• upstream_timeout_ms default raised 300000→1800000 (30 min):
  the prior 5-minute ceiling was too aggressive for long-running
  reasoning models.

• ttft_retry_max_attempts default 2→3: one more retry before
  giving up, enabled by the smarter threshold.

• ttft_retry_cooldown_ms default 30000→5000: shorter cooldown
  between attempts now that false-positive kills are less likely.

Added

• ttft_watchdog_multiplier (default 5): multiplier applied to the
  model's p50 TTFT to compute the dynamic threshold.
• ttft_watchdog_hard_cap_ms (default 300000): hard cap on the
  dynamic threshold; also used as the attempt 2+ threshold.
• src/status-client.ts: fetches /v1/status with shared-promise
  dedup, 5-second timeout, and model bridging chain (direct model →
  base_model.name via ModelsClient → overall p50 → null).
• DB columns upstream_ttft_p50_ms + upstream_tps_p50 on
  captures table, propagated through CaptureSummary, CaptureRow,
  ResponseMeta, and the dashboard.
• ADR-0026 (smart TTFT watchdog) and ADR-0027 (upstream timeout
  default).

Removed

• ttft_retry_failure_threshold and
  ttft_retry_failure_window_ms config fields: dead under the new
  design (no auto-disable, no failure window).
• src/experiments/ttft-watchdog-state.ts: the auto-disable state
  machine is gone. The watchdog is always armed when
  experiment_ttft_watchdog is enabled.
• Dashboard "watchdog off" badge: removed from gate-status.tsx.