* Fix UTF-8 startup option precedence and refresh canonical tests
Resolve the first explicit UTF-8 option before environment validation and align startup diagnostics with CPython 3.15. Refresh canonical encoding tests through update_lib and narrow the existing environment test failure to Windows. Support only monotonic expected-failure narrowing in updater metadata with focused regression tests.
Assisted-by: OpenAI Codex: model version unavailable
* Normalize configured standard-stream codec names
Resolve explicit stdio encodings through CodecInfo.name before creating standard streams, matching CPython initialization. Preserve ordinary TextIOWrapper spelling and existing standard-stream error policies; leave canonical tests unchanged.
Assisted-by: OpenAI Codex: model version unavailable
* Retire passing standard-stream UTF-8 expected failure
The configured-codec normalization fix makes canonical test_stdio pass in both Linux CI attempts. Remove only its stale expectedFailure through update_lib, preserving canonical assertions and all other platform guards.
Assisted-by: OpenAI Codex: model version unavailable
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Co-authored-by: Codex <codex@openai.com>
