GeezerVison

Two existing Python 3.14 paths violate runtime object contracts: disabling standard I/O creates fresh None objects, and conditional-annotation tracking assumes a user-rebindable global is an exact set.

Return the context's None singleton for all six disabled stream attributes, and validate the set operand before adding an annotation name. Include an embedding regression that actually runs without the stdio feature, and the unchanged canonical annotation regression from CPython's 3.14 maintenance backport.

Extracted from #8954 onto main f39b054b9c8cbbf884f53123eef028131789990c, retaining the unchanged Python 3.14 target. The mega PR retains these fixes until they are merged independently. No marshal or Python 3.15 behavior is included.

Fresh standalone validation on 8aeae47903cd431fcb31237597ae216c80512f65:

• Rust workspace: 1,345 passed /18 ignored; separate C-API: 116 passed /4 ignored
• Explicit no-stdio feature build: no_stdio_streams_are_none_singleton executed and passed (1 test); default builds compile it out
• Both Clippy gates pass without warnings, release build passes, and runtime identity confirms Python 3.14 at this head
• Full test_type_annotations: 49 run /1 skipped; test_setcomps: 2 run; test_site: 43 run /6 skipped. All complete successfully
• Existing syntax_annotations_locals.py and builtin_set.py pass
• Normal configured commit hooks pass; no existing assertions or expected-failure markers changed

The official annotation backport commit c21e7c45a9770fba9ea3b8d5abb52c19274a08ef is after CPython 3.14.7. The released 3.14.7 reference still crashes on that exact canonical regression; this is a maintenance fix, not a claim that the vulnerable released tag passes. The corrected native regression passes; the reference crash was not repeated.

AI assistance: prepared, reviewed and tested with Codex at the user's direction. Exact model metadata is unavailable; the commit records Assisted-by: Codex:model-version-unavailable.