Propagate TLS alert error codes

[SC123667]

Summary

• map TLS alert descriptions to QUIC CRYPTO_ERROR codes in the reserved 0x100..=0x1ff range
• preserve the TLS session's precise close error when propagating handshake failures to the connection
• extend the ALPN mismatch regression test through both the local close state and the peer's decoded CONNECTION_CLOSE

Root cause

BoringSSL recorded the specific 0x100 + alert code in TlsSessionData, but Connection::process_tls_session never copied it into local_error. The generic receive error path then closed the connection with TlsFail::to_wire(), which fell back to NO_ERROR (0x0).

Testing

• cargo fmt --all -- --check
• cargo clippy --all -- -D warnings
• cargo clippy --all -F ffi -- -D warnings
• cargo test --verbose (558 unit tests and 1 doc test)
• cargo build --all -F ffi --verbose
• cargo test --no-default-features (388 unit tests and 1 doc test)
• cargo test --no-default-features -F ffi,qlog,h3 (558 unit tests and 1 doc test)
• typos -c ./typos.toml

Resolve #243