Preserve table grid widths for LibreOffice 6.4

[FuqingZh]

Summary

• preserve positive Word table-grid widths while retaining content autofit
• add an opt-in real LibreOffice conversion regression probe
• prepare version 0.1.5 and replace tag-push publishing with GitHub Release-driven trusted publishing
• verify release source and wheel/sdist identities before PyPI publication

Local verification

• Ruff: passed
• Pyright: 0 errors
• Pytest: 87 passed, 1 skipped
• Real LibreOffice compatibility probe: 1 passed on LibreOffice 6.4.7.2
• PDM build: passed
• Release artifact identity, Twine, wheel install, and sdist-wheel rebuild probes: passed