fix(http-client-python): generate valid Python type annotations in types.py

[Libba Lawrence (l0lawrence)]

The Python client emitter generated types.py files with invalid type annotations for azure-search-documents, producing 4 MyPy errors across three generated files. This fixes the three distinct codegen bugs behind them.

What was wrong and how it's fixed

1. Internal enum annotation/import mismatch. An internal enum used as a TypedDict field was annotated as _enums.Name while _enums was never imported (and the enum is not re-exported from the public models package), yielding Name '_enums' is not defined and Module has no attribute errors. The enum is now imported as a bare symbol from its private _enums submodule, and the TYPES_FILE annotation drops the undefined _enums. prefix. Enums stay private (no change to the public __all__).

2. Duplicate enum import. The same symbol could be imported once at runtime and again under if TYPE_CHECKING: (from different modules), triggering mypy no-redef. Added a dedup pass that drops a TYPE_CHECKING submodule import when its bound name is already imported at runtime; the runtime import is sufficient for the annotations.

3. TypedDict requiredness override via inheritance. A child TypedDict that redeclared an inherited field with different requiredness produced Overwriting TypedDict field ... while extending, which PEP 589 forbids. Such models are now emitted as a flat, non-inheriting TypedDict that lists every field (inherited plus own) directly, so requiredness is expressed without subclassing.

Notes for reviewers

• The internal-enum import intentionally imports the bare symbol from _enums rather than the _enums module, which also avoids name collisions when internal enums come from several sibling namespaces.
• Regression tests were added to tests/unit/test_typeddict.py covering all three cases.

Validation

• test_typeddict.py + test_enums.py: 50 passed (42 existing + 8 new).
• pylint 10.00/10 on the changed files; black clean under the project config; mypy introduces no new errors (the pre-existing errors are unchanged on the baseline).

Fixes: #11626

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npm i https://pkg.pr.new/@typespec/http-client-python@11627

commit: 708a666

[github-actions]

All changed packages have been documented.

• ✅ @typespec/http-client-python

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@typespec/http-client-python - fix ✏️

Fix invalid Python type annotations generated in types.py files. Internal enums used as TypedDict fields are now imported (as a bare symbol) from their private _enums submodule so the annotation resolves; duplicate runtime + TYPE_CHECKING imports of the same symbol are deduplicated to avoid no-redef; and TypedDicts that change an inherited field's requiredness are emitted as a flat (non-inheriting) TypedDict to satisfy PEP 589.

[azure-sdk-automation]

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[Libba Lawrence (l0lawrence)]

Reopening as a same-repo PR (branch pushed to microsoft/typespec) so the emitter-diff CI check runs.