feat(http-client-python): export TypedDicts from namespace-root __init__.py

[l0lawrence]

Problem

In dpg and typeddict models modes, generated TypedDicts (and their Union/Literal aliases) are written to types.py, but they were never re-exported from the namespace-root __init__.py — only clients and __version__ were. As a result, from <package> import MyModel did not work; the TypedDicts were only reachable via the implicit types submodule (from <package> import types; types.MyModel).

Change

• general_serializer.py — added typeddict_names_for_init(), which mirrors the exact gate and name-selection used to generate types.py (literal_enums + discriminated_base_models + typeddict_models via TypesSerializer) so only names that actually exist in types.py are imported. Returns [] for the async (aio/) init since types.py lives at the namespace root. serialize_init_file now feeds these names to the template.
• init.py.jinja2 — emits from .types import (...) and adds the names to __all__ when present.

This covers both DPG mode (TypedDict copies of input models, base="typeddict") and typeddict mode (all models as TypedDicts).

Result

from my_package import MyModel  # previously only reachable via `from my_package import types`

Tests

Added 4 unit tests in test_typeddict.py:

• typeddict-mode init re-exports TypedDicts
• dpg-mode init re-exports TypedDict copies
• async (aio/) init does not import from .types
• no-types case emits no .types import

Validation

• New + existing typeddict tests: 17 passed
• black formatted, pylint 10.00/10
• The 3 unrelated tests/unit failures (XML/model_base serialization) are pre-existing and reproduce on a clean checkout
• Generated SDK output is not git-tracked, so no regeneration is required
• Added a feature chronus changelog entry

[github-actions]

All changed packages have been documented.

• ✅ @typespec/http-client-python

Show changes

@typespec/http-client-python - feature ✏️

Export generated TypedDict types (and their Union/Literal aliases from types.py) from the namespace-root __init__.py in dpg and typeddict models modes, so they can be imported directly from the package:,> ,> python,> from my_package import MyModel # previously only reachable via `from my_package import types`,>

[l0lawrence]

Retargeting to microsoft/typespec:main.