fix(#828): handle broker connections concurrently with per-conn deadlines + bounded concurrency

docs/scratchpads/828-lease-broker.md

@@ -76,6 +76,9 @@ Verified before code on session start; all exact SHA-256 values matched:
 - Post-remediation evidence: Python unit suite `10/10`, focused real-socket acceptance `35/35`, full root suite `43/43` Turbo tasks, broker coverage `90%` (`395` statements, `38` missed), lint `23/23`, typecheck `42/42`, format check and `git diff --check` GREEN.
 - Independent Codex review of remediation commit `d05465e54736c4966294c4af8fbd6a4ad8fe81aa`: APPROVE, confidence `0.94`, zero findings. Reviewer sandbox could not allocate temp directories; unrestricted parent test evidence above is canonical.
 
+- Remediation session: terra review comment `18072` reproduced a SERIAL-ACCEPT DoS; scope is RED regressions plus bounded concurrent connection handling on PR #836, preserving all existing broker security properties.
+- RED evidence against reviewed daemon: four silent peers delayed registration `3920 ms` beyond the `1500 ms` bound; 16 silent peers were not reaped within `2500 ms`. The first bounded implementation then exposed slot exhaustion by rejecting the valid queued caller with `EPIPE`; admission was corrected to wait for a reclaimed bounded slot. GREEN evidence: queued-peer test `211 ms`; strengthened cap/reap/reclaim test `1118 ms`; complete real-socket acceptance `37/37` and Python persistence suite `10/10`.
+
 ## Coordinator handoff requirements
 
 1. Mandatory Opus-SECREV on the exact PR head; no GPT/terra substitute.