## Summary
- require a Pong within 60 seconds for established Noise Rendezvous
WebSockets on both the harness and executor
- bound steady-state WebSocket writes and harness event delivery so
backpressure cannot mask the deadline
- classify executor disconnects with bounded reasons and feed them into
the existing reconnect metric and structured log
- cover silent peers, responsive peers, continuous non-Pong traffic, and
local application backpressure
## Why
The existing periodic Pings did not track Pongs, so a half-open or
blackholed connection could remain stuck until the operating system's
TCP timeout. This adds the smallest explicit liveness contract without
new spans, RTT histograms, feature flags, or TCP diagnostics.
## Testing
- `just test -p codex-exec-server` on devbox `richard-6` — 300 passed, 2
skipped
- `just fix -p codex-exec-server`
- `just fmt`
- independent correctness, performance/security, and YAGNI reviews — no
findings
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