feat(icons): 한칸 on a jade ground

The PWA manifest declared icon-192.png, icon-512.png and favicon.svg. None
of the three existed, so install-to-home-screen and the browser tab both
resolved to nothing. That was a defect in what the last pass claimed as
done.

Drawn procedurally with Pillow rather than authored as SVG: there is no
dependable SVG rasteriser here to convert from, and ImageMagick falls back
to its MSVG renderer, which cannot be trusted with text. Pillow's
FreeType + RAQM stack shapes Hangul correctly, which is the only hard
requirement. The mark uses the app's own register — the serif face already
used for 한칸 on the boot screen, in --jade on --bg.

Two glyphs read well at 180px and up; at favicon sizes 한칸 turns to mush,
so the small sizes carry 한 alone.

  icon-192 · icon-512 · apple-touch-icon (180)   한칸
  icon-512-maskable                              한칸 at 56%, inside
                                                 Android's circular crop
  favicon.ico (16/32/48) · favicon-32            한

Sizing is a binary search on the drawn ink extent, and centring uses the ink
bounds rather than the font's line box — CJK metrics leave asymmetric space
above and below, which would otherwise sit the mark visibly high.

Re-running the generator writes byte-identical files.

Android launcher icons are untouched; Android work is out of scope.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

This commit is contained in: