[cppla]

Summary

• Close native QUIC/TLS TCP destinations when the physical connection or server owner ends, including idle reads after an upload FIN.
• Stop or join the owner callback before releasing stream admission; preserve ordinary bidirectional half-close.
• Use the physical QUIC connection context rather than its send-side stream context; keep dialing cancellation independent.
• Stabilize one existing trailer fixture with a test-only bounded retry for typed UDP ephemeral-port collisions. Fixed addresses, other errors, and joined rollback failures remain fail-fast; production ListenWeb is unchanged.

Validation and retained failures

• Frozen real TCP/TLS1.3/QUIC fixture: original implementation failed all 8 shutdown cases and both Close callback cases; all 4 healthy half-close controls passed. Independent target cleanup joined every worker.
• Negative mutations rejected: send-side-context owner loses post-FIN upload; omitted callback join releases admission early; disabled ephemeral setup retry fails with a real occupied UDP endpoint after directly proving TCP rollback. Correct hashes restored afterward.
• Latest combined selection: 8 top tests, 63 runtime nodes, race x10 each on Go 1.25.13 and 1.27.1 with exact 630 RUN/PASS entries per log. Full make check and make race passed again.
• Latest-source Linux/arm64 isolated Docker x3 passed: all 8 top tests / 63 runtime nodes, exact 189 RUN/PASS entries, 0 FAIL/SKIP (CGO=0, non-race). Fresh binary and all source/input/compiler/driver guards matched; dedicated container was removed. Earlier owner-only run and an initial corrected host-driver awk preflight error are retained separately.
• First PR head 064875d CI run 37096137959 failed Go 1.25 job 111126350337: existing trailer public_origin setup's TCP-selected port was already occupied in UDP. Original failure retained; no rerun or merge of that head. Test-only correction is a new commit with fresh CI.

No authentication, protocol, dependency, default timeout or UDP production changes. No release/tag/image publication or remote SSH testing. Latest public CI and post-merge main are independent gates.

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