Improve serverless wake readiness logs

[techulus-agent]

Summary

• make serverless wake readiness checks return structured wait reasons instead of a bare boolean
• log blocking/background wake wait reasons with attempt count, elapsed time, container state, health state, upstream, dial latency, and dial error
• include the last wait reason on wake timeout transitions and add status report latency logging

Why

Cold starts were showing a long gap between wake container started and wake ready with no explanation. For apps without health checks, the gateway was still waiting on TCP reachability, but the logs did not say whether the delay was container state, health state, or upstream dial failure.

Validation

• GOCACHE=/private/tmp/codex-go-cache go test ./... from agent/

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit dd3c405.}