Replace the hardcoded 30s webhook agent-run deadline with a configurable
timeout (default 600s, cap 3600s) for both the async worker and the
sync/test HTTP handler. Legitimate multi-step runs were dying at 30s
mid-tool-call; the same request over WebSocket completed fine.
- internal/webhooks/timeout.go: ResolveTimeoutSec helper (<=0 → 600s, cap 3600s)
- WorkerConfig.AsyncAgentTimeout (async worker) + WebhookLLMHandler.syncTimeout
(sync + admin test), wired from config
- config keys gateway.webhook_{async,sync}_timeout_sec, also settable via
GOCLAW_WEBHOOK_{ASYNC,SYNC}_TIMEOUT_SEC env (env overrides config)
- tests: timeout bounds + config file/env override
