docs: close out v1.2.1 Windows hotfix

[tsubotti63]

Summary

• align active public documentation with published stable v1.2.1
• replace the temporary v1.2.0 Windows workaround with bounded post-release evidence
• record the Windows validation workflow policy, CS-008, and release closeout
• update the public-command validator and regression tests

Windows evidence

One maintainer-owned physical Windows environment clean-installed Production
PyPI v1.2.1. tzdata 2026.3 installed automatically, Asia/Tokyo resolved,
and the tracked Synthetic Run-All completed with PASS_WITH_WARNINGS, exit 0,
Activities detected=1 / processed=1, and run_summary.json present. No manual
pip install tzdata, local install, or editable install was used. This is
bounded evidence and not a universal Windows compatibility claim.

Validation

• Unit Test: 129 passed
• pytest: 158 passed
• bootstrap, static policy, platform alignment, schema contract, and public command validator: PASS
• public history validator: PASS in a normalized CI-ref clone
• package build: PASS
• twine check --strict: PASS

Boundaries

• no tag, GitHub Release, or PyPI changes
• no personal Garmin data or Windows host identity
• no universal Windows support claim
• merge remains Human-controlled