[Lucas1479]

Old uv-managed macOS Python builds can pass the package verifier but fail VN portrait startup at Tk initialization or Pillow ImageTk transfer. Document uv-managed CPython 3.12.14 and a reversible existing-.venv migration, and qualify the actual native image boundary in macOS CI.

• Add a standalone, asset-free probe that creates/withdraws a Tk root, transfers a generated RGBA image through ImageTk, verifies dimensions/pixels/transparency, and destroys the root. Failures return nonzero with the failing stage and migration guidance.
• Make the macOS voice/desktop job explicitly create its application environment with uv-managed 3.12.14, retaining setup-python only to bootstrap uv. Run the native probe against the current locked Pillow 13.0.0. Keep ordinary package/profile checks usable without a display.
• Give both English and Chinese READMEs separate Windows/macOS environment-creation commands, with the macOS interpreter and existing-environment migration guidance before creation. Add the native-portrait-only graphical-session check to the macOS preflight checklist and document the probe in the maintenance tool index. Preserve the existing renderer and dependency lock.

Refs #223. Keep the issue open for the reporter's complete macOS VN Start acceptance; this PR does not close it automatically.

Validation:

• 97 related tests passed with the existing development environment (UV_OFFLINE=1 python -X utf8 -m pytest -q tests/test_vn_portrait_environment.py tests/test_python_environment_verifier.py tests/test_profile_contract.py tests/test_core_install_tiers.py tests/test_vn_portrait_shared.py tests/test_vn_overlay_window_contract.py tests/test_vn_overlay_continuity.py).
• Native probe passed on Windows AMD64 / CPython 3.12.10 / Tcl/Tk 8.6.15 with both Pillow 12.3.0 and 13.0.0; the six new diagnostic tests also passed in the isolated Pillow 13.0.0 environment.
• Repository Ruff, architecture views, generated README overview, and diff whitespace checks passed.
• macOS CI passed on fa27de77: Darwin arm64, uv-managed CPython 3.12.14 (Clang 22.1.3), Pillow 13.0.0, Tcl/Tk 9.0.4. The real native RGBA probe passed; 281 contract tests passed (2 skipped), and Electron build and model-less desktop smoke passed.
• All 15 PR checks passed on fa27de77c23bce07766d4d679c564613bb8dd495, including the three complete Python-suite partitions, Windows source/packaged desktop smoke, Linux and macOS desktop checks, and all installation profiles. Full game/OCR/audio acceptance remains with VN portrait fails to start on macOS with uv-managed Python 3.12.10 #223.
• Documentation-only follow-up b160d8ab: generated README overview and diff whitespace checks passed; both language entry points and the conditional preflight command were reviewed for consistency. Runtime, probe, tests and CI configuration are unchanged from the qualified commit above.
• CI history for b160d8ab: the first Windows partition 2 run failed in the unchanged test_pi_cancel_cleanup.py error-publication case while decoding an empty finally.json. Three local runs of that file produced two complete passes, then a different permission-event startup timeout (8 passed / 1 failed overall); they did not reproduce the empty-JSON failure. No Pi code or assertions were changed. The single same-commit rerun passed the full partition, including all three Pi cancellation tests. All 15 checks are now successful on b160d8abb22fedfe788faded237efe721e700b78. The cause of the intermittent Pi integration-test results remains unestablished; this PR does not claim to fix it.