fix(readme): three different contract counts, and the guard that watches them ran nowhere

[noahgift]

README claimed 1771 provable contracts in its metrics table (correct), 1158 at
line 225, and 1767 at line 256. Filesystem: 1771 .yaml, 0 .yml.

scripts/check_readme_claims.sh implements FALSIFY-README-00* precisely to stop
this, and it could not:

1. It ran NOWHERE. Not in any workflow, not in the Makefile. Its only caller in
   the entire tree is scripts/dogfood-book.sh:112, and dogfood-book.sh is
   itself in no workflow and no Makefile target -- unreachable from anything.
2. It matched only **M** provable contracts, the bold table form, then took
   head -1. The prose forms at lines 225 and 256 were invisible to it, and
   even a second bold claim would have been dropped by the head.

So the one claim it checked was the one that happened to be right. A drift
detector that is both unwired and pattern-narrow supplies the APPEARANCE of claim
discipline, which is worse than no detector -- a reader of the README has no way
to know which of three numbers to believe, and nothing in CI made any of them
true.

Fixes:

• README lines 225 and 256 corrected to 1771.
• claimed_contract_counts returns EVERY contract-count claim (a number
  optionally followed by up to two qualifier words, then "contract(s)"), and
  all of them must equal the measurement. The README is no longer permitted to
  contradict itself, which is a stronger property than matching the filesystem
  once. On failure it prints the offending lines with line numbers.
• Wired into the merge-blocking guard block.

Mutation-verified, each RED then restored GREEN:

• drift ONLY the line-256 prose claim -- the form the old guard was blind to
• drift the line-44 table claim -- the form it did see

Refs #2481

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