Synchronous dispatch() now converts office documents via OnlyOffice
(asyncio.run around OOConversionManager.convert), refusing to run inside
a live event loop and pointing async callers at
pool.generate_office_preview(). The office import stays lazy so the base
install works without the 'office' extra.
Unknown file types now name the offending extension (or its absence)
instead of a generic 'preview unsupported'.
Worker logs expected PreviewError failures as warnings; tracebacks are
reserved for unanticipated internal errors. pdf read errors report
backend "pdf" (vips not yet reached); the stage field is dropped as the
backend name now encodes the failing pipeline step. Backend label
"pyvips" renamed to "vips" everywhere.
Add fixtures and tests covering image EXIF orientations, HDR AVIF, SDR video, 90/270 rotated video, HDR video with and without rotation, PDF, dispatch, and OnlyOffice (skipped unless configured).
Regenerate rotated/HDR video fixtures and sample.pdf with tests/files/generate_fixtures.py.