fix(gallery): regenerate the 25 drifted heroes from their code, with contact sheets (#225)

#200's full sweep found 25 committed heroes that no longer matched what
their scripts render (3.8-77% of pixels past 2% against a q90 re-encode of
the fresh render); the other 54 matched at the encode floor. Several
scenes had been edited after their still was made, and the PNG-to-webp
step lived in uncommitted scratch scripts, so nobody could regenerate a
still and get the committed result.

- scripts/render_hero.py: the one committed path. Renders an entry's README
  --output command (the script's own framing/asset gates run first) and
  writes the hero (1280x720) and preview (1200x675) as webp q90.
- scripts/contact_sheet.py: builds the contact sheet in the committed
  format and prints each tile's luma, stage, wedge warmth and saturation.
- The 25 heroes and their previews are regenerated on Blender 5.2.1 LTS;
  re-measured, all 25 now match their code (0.00-0.04%).
- Contact sheets for those 25, plus the 8 matching showcase pieces that had
  none (#202), against the regenerated calibration set.
- assets/og-card.jpg rebuilt from the regenerated heroes.
- CLAUDE.md names the three tools under the contact-sheet gate.

Closes #200

Signed-off-by: TMHSDigital <154358121+TMHSDigital@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: TMHSDigital