fix: support Windows timezone data and onboarding

[tsubotti63]

Summary

• add Windows timezone-data support for Asia/Tokyo
• improve bounded diagnostics for missing timezone data
• add Windows PowerShell onboarding paths
• add Windows Synthetic Run-All CI coverage
• add regression validation for public command examples

Root cause

Stable v1.2.0 declared no runtime dependencies. On a third-party Windows
environment, Python zoneinfo could not resolve Asia/Tokyo, causing
Activities normalization to fail. Manually installing tzdata restored the
tracked Synthetic Run-All.

Evidence

• reproduced on one third-party Windows environment
• ZoneInfoNotFoundError before tzdata
• PASS_WITH_WARNINGS, exit 0 after manual tzdata
• Activities detected=1 / processed=1
• run_summary.json generated

Validation

• Windows PowerShell setup now uses python -m venv .venv as the primary path
• isolated wheel install completed the tracked Synthetic Run-All
• isolated sdist install completed the tracked Synthetic Run-All
• both packaged flows produced PASS_WITH_WARNINGS, exit 0, and run_summary.json

Boundaries

• no claim of universal Windows validation
• no Tag, Release, or PyPI publication
• no personal Garmin data
• stable output semantics unchanged