docs: include img2threejs in stocktake audit table and sync readme diagram

[kuker24]

Summary

Closes the leftover stocktake audit gap in docs/stocktake-1.8.3.md without changing existing verdicts or bumping versions.

• docs/stocktake-1.8.3.md:
  • Update intro: measured tree is now 47 model + 16 manual = 63. Cites 66eebe9 / PR feat: adapt AI LABS wave (img2threejs, optional reticle & ui-skills MCPs, anti-slop merge) #21; earlier rows were taken against 4b1fd7f2 / chore: sync catalog counts and sharpen stocktake verdicts #18 protocol.
  • Insert row for img2threejs (KEEP, model-invoked) in alphabetical order after hyperframes.
  • Update tallies: 57 KEEP, 2 COMPRESS, 4 UPDATE, 0 MERGE, 0 RETIRE, Total 63.
  • Note in follow-ups: img2threejs added post-feat: adapt AI LABS wave (img2threejs, optional reticle & ui-skills MCPs, anti-slop merge) #21; not part of the original 1.8.3 execution pass.
  • Recounted and verified by parsing table rows via script.
• CHANGELOG.md:
  • Add bullet under ## Unreleased documenting img2threejs inclusion in the stocktake doc (63 rows, KEEP).
• README.md:
  • Sync architecture diagram from 46 automatic to 47 automatic.