v0.23.1

Performance

• A bottom-up BMP (the common kind) read from a file is read from its end a block of rows at a time instead of whole: bmp -> png on a 61 MB photo holds 5.6 MB instead of 66 and runs 2.6% ahead of the crates (it had slipped 1.4% behind in 0.23.0). Converter inputs that are files can now seek (RewindableRead::seek_to).
• The PNG writer's per-row calls are inlined again (0.23.0's shared FilteredZlib had lost it).

Fixed

• Images to PDF: a page takes the image's physical size from the resolution it records (PNG, JPEG, TIFF, BMP), so a 300-dpi scan becomes a letter-sized page rather than one a point per pixel; images without one stay a point per pixel. Readers report resolution through RowSink::density.

Changed

• The format map in DOCS/FORMATS.md (sublime paths --markdown) is readable at size: a graph shows only which formats convert directly, one plain line per pair. Under each graph a from-by-to grid gives every pair's fidelity as a shape (a filled circle lossless, a square half filled on the diagonal conditional, a hollow triangle lossy; DOCS/map/) and its number of steps.
• DOCS/FORMATS.md opens with the map, lists formats in a table per category, and escapes angle brackets in notes (a note's <root> no longer disappears on GitHub).