feat: v2.5.0 — sliding-window circuit breaker, graduated backoff, increased timeouts

Emergency fix for multi-agent (ClawTeam) burst scenario that caused cascading
failures: when multiple Opus agents ran concurrently, the old consecutive-count
breaker (threshold=3) tripped within seconds, blocking ALL subsequent requests
globally — including non-ClawTeam agents and new sessions.

Changes:
- Circuit breaker now uses a sliding time window (default 5min) instead of
  consecutive failure count. 6 failures in 5min triggers open, vs old 3-in-a-row.
- Half-open state allows 2 concurrent probe requests (was 1), improving recovery
  speed when API comes back.
- Graduated backoff: cooldown doubles on each re-open (120s→240s→300s cap),
  resets fully on first success.
- Increased default timeouts: Opus first-byte 60s→90s, Sonnet 45s→60s,
  overall 120s→300s, max concurrent 5→8.
- /health endpoint now exposes per-model breaker state, window stats, and
  marks status as "degraded" when any breaker is open.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "openclaw-claude-proxy",
-  "version": "2.4.1",
-  "description": "OpenAI-compatible proxy for Claude CLI v2 — per-model circuit breaker, adaptive first-byte timeout, structured logging",
+  "version": "2.5.0",
+  "description": "OpenAI-compatible proxy for Claude CLI v2 — sliding-window circuit breaker, adaptive first-byte timeout, structured logging",
   "type": "module",
   "bin": {
     "openclaw-claude-proxy": "./server.mjs"