Enable ruff typing-only import rules (TC)

[anth-volk]

Fixes #3901

Summary

Phase 1 step 1.8, group 2: typing-only imports. Stacked on #3898.

• What changed: select gains TC, and about 400 fixes move imports used only in annotations under TYPE_CHECKING. This removes import-time work and import cycles, without changing runtime behaviour.
• What stays at runtime: Pydantic and SQLModel models, SQLAlchemy declarative models and FastAPI endpoints all evaluate annotations at runtime, so their imports must stay. [tool.ruff.lint.flake8-type-checking] lists:
  • Runtime-evaluated base classes: pydantic.BaseModel, sqlmodel.SQLModel, sqlalchemy.orm.DeclarativeBase, V1Base, and every project model class that other models inherit from (35). Ruff checks direct bases only, so each must be listed. A new model base that's missing from the list is caught by the test suite, which builds every model and route.
  • Runtime-evaluated decorators: the APIRouter route decorators.
• Found during testing: the first attempt broke V1Base models, because SQLAlchemy resolves Mapped[...] at class creation. Hence DeclarativeBase and V1Base are on the list.
• Shared tool: scripts/rules changes are mirrored in sim, so the tool stays byte-identical.

Testing

• pytest tests/unit tests/contract: 2,358 passed. tests/to_refactor and the in-flight dedupe test: 53 passed, the same as the base branch.
• mypy is clean. ruff check . passes with 0.15.12 and 0.16.8.
• Rules tool unittest passes on Python 3.11, 3.12 and 3.14. All guards pass.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 26.25369% with 250 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.64%. Comparing base (172bbed) to head (11c3b1f).

Files with missing lines	Patch %	Lines
...cyengine_api/services/v2/user_policies/services.py	14.28%	5 Missing and 1 partial ⚠️
...pi/services/v2/comparison_runs/database_session.py	0.00%	5 Missing ⚠️
...olicyengine_api/services/v2/households/services.py	16.66%	4 Missing and 1 partial ⚠️
policyengine_api/services/v2/policies/services.py	16.66%	4 Missing and 1 partial ⚠️
...engine_api/services/v2/policies/transformations.py	16.66%	4 Missing and 1 partial ⚠️
...engine_api/services/v2/user_households/services.py	16.66%	4 Missing and 1 partial ⚠️
policyengine_api/asgi_factory.py	20.00%	3 Missing and 1 partial ⚠️
policyengine_api/data/v2/catalog/records.py	20.00%	3 Missing and 1 partial ⚠️
policyengine_api/data/v2/report_runs.py	20.00%	3 Missing and 1 partial ⚠️
policyengine_api/fastapi_routes/dependencies.py	0.00%	4 Missing ⚠️
... and 79 more

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3902       +/-   ##
===========================================
+ Coverage   45.27%   85.64%   +40.36%     
===========================================
  Files         183      198       +15     
  Lines       11084    12355     +1271     
  Branches     1907     2247      +340     
===========================================
+ Hits         5018    10581     +5563     
+ Misses       5644     1093     -4551     
- Partials      422      681      +259     

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