[cppla]

Summary

• Preserve an authenticated HTTP/2 connection when its stream limit is temporarily full, across the legacy and Go 1.27 native transports.
• Treat native state only as a conservative queue hint. An authoritative pre-HEADERS rejection can reselect once within the original caller deadline; encoded requests, bootstrap authentication and canceled requests are never replayed.
• Keep transport inspection outside the session-owner lock, preserve accepted sibling streams when retiring a draining connection, and document these ownership rules.

This follows the first-attempt main CI failure after #62. A frozen real-TLS/MAX_CONCURRENT_STREAMS=1 control reproduces the old-source session replacement on Go 1.27 and passes on Go 1.25. The original failed CI and local diagnostic remain retained separately.

Validation

• make check and make race: passed.
• Seven focused top-level regressions, race/count20, on Go 1.25.13, Go 1.27.1 and Go 1.27.1 with http2legacy: all passed.
• The unchanged previously failing H2 leaf, original seed, coverage/count100: 100/100 passed.
• Fresh isolated Linux/arm64 Docker execution, seven focused tops/count3: all passed.
• Four new controlled regressions cover queued cancellation, capacity release, ordered GOAWAY, and a protocol reset after encoded HEADERS with no automatic replay.

No dependency, wire protocol, default configuration, workflow, version or release change. These checks establish the tested lifecycle behavior, not browser equivalence or performance claims.

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