Replace RootModel wrappers with type aliases and TypeAdapter validation
Replace the reintroduced RootModel wrappers with plain types and unions validated by TypeAdapter, following #1910. Update code generation and enforce Ruff's TID251 ban for both import paths, including generated files.
How Has This Been Tested?
The full suite passes with 5,968 tests and 100% line and branch coverage; strict-no-cover passes. The focused suite passes all 605 tests on Python 3.10, and Ruff, Pyright, the lockfile check, and regeneration checks pass.
Breaking Changes
Wire formats are preserved. FuncMetadata.output_model for dictionary returns now holds a type annotation instead of a model class; validate it with TypeAdapter. The AnyUrlModel authorization helper is removed.
AI Disclaimer
This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.