Migrate core runtime tests to source-relative unit modules

[juliendenize]

Summary

Move core model, deprecation, and optional-dependency tests out of the legacy test root into source-relative unit modules. Preserve every existing assertion while adding focused checks for shared base-model behavior and small runtime utilities. This PR changes tests only; production behavior and public APIs are unchanged.

Changes

• Relocate base, deprecation, and import assertions to tests/unit/; retain concrete message and chunk filtering cases, warning-key behavior, both cached import states, and exact dependency hints.
• Use three named pytest parameter cases for the independent empty-base, user-extra-name, and text-extra-annotations filter mappings. Each case retains the original explicit input and full expected result. Keep the stateful warning-key sequence together.
• Add focused checks for inherited and nested model validation, broken OpenCV imports and custom errors, exception messages, and deterministic UUID generation.
• Keep the intentionally invalid string default for runtime validation, using only a line-local # type: ignore[assignment]. Assert the exact field and input in its ValidationError while retaining a passing mypy gate.

Review tests/unit/test_base.py for the named filter mappings and model boundary, then tests/unit/test_deprecation.py and tests/unit/test_imports.py for preserved assertions, and finally the new exception and protocol utility tests. No source, CLI, configuration, or contributor-guidance file is changed.

Verification

• Python 3.12: five focused unit modules, 42 passed both serially and with -n auto --dist loadfile; 12 base nodes include all three named filter cases.

• Full pytest tests/ -q: 1,776 passed, 16 skipped.

• ruff check tests and ruff format --check tests: passed; 74 files formatted.

• mypy .: passed across 122 source files; pytest --doctest-modules ./src: 53 passed.

• Python 3.10–3.14 CI collection and execution remain to be verified: the repository workflow skips its test jobs while this PR is a draft.

• Tests added or updated for changed behavior

• Documentation and public API examples updated where needed (not applicable: test-only changes)

• Ruff, mypy, and pytest checks pass locally