v1.6.2 — content-hash staleness for Office, PDF and image files

Fix

• akf check no longer reports STALE after a fresh checkout for DOCX, XLSX, PPTX, PDF and PNG files, and for JPEG/WEBP/TIFF stamped with older sidecar stamps (#145). Stamps record meta.content_hash (content with the embedded stamp removed) and check compares it instead of relying on file mtime alone.
• 1.6.1 already covered Markdown and sidecar-stamped code files.

Restamp existing Office/PDF/PNG files with 1.6.2 to record the hash; other formats keep the mtime rule.

pip install -U akf