⬆️ chore: require Python 3.11 and test Python 3.15/3.15t

[ShigureNyako]

Changes

Minimal Python-support update (four files):

• pyproject.toml: require Python 3.11+, replace the 3.10 classifier with 3.15, align Ruff's target, and remove the unreachable <3.11 tomli dependency.
• uv.lock: regenerate for that floor. No dependency versions change; the deletions remove obsolete tomli/exceptiongroup entries, <3.11 dependency edges, and Python 3.10 wheels.
• Existing lint matrix: 3.10 → 3.11.
• Existing test matrix: drop 3.10 and add 3.15/3.15t. Set UV_PYTHON to the matrix value so uv selects the requested interpreter, including the free-threaded build.

No README, justfile, source, test, new workflow, or dependency-upgrade changes. The previously added runtime-assertion step and locked-mode recipe changes have been removed; interpreter/GIL verification remains local validation evidence, not extra repository code.

Validation

• Normal locked development dependencies and all 34 tests pass on each of 3.11, 3.12, 3.13, 3.14, 3.15.0rc2, and 3.15.0rc2 free-threaded.
• Local 3.15t verification: free-threaded build, with the GIL disabled before and after pytest.
• Wheel/sdist builds and fresh wheel CLI smoke tests passed; Python 3.10 installation is rejected by the updated metadata.
• uv lock --check, Ruff lint/format, ty, actionlint, and git diff --check pass.

Python 3.15 is a prerelease, but no dependency prereleases or dependency bypasses are needed (no Pydantic dependency). CI results: checks.

Targets ShigureLab/dochooks only; separate from the merged Renovate configuration PR #1.