The register at libs/shared/docs/cibg-gaps.mdx had 8 rows for 9
CIBG-GAP EXTENSION markers in code. language-switcher carries a
well-formed marker with no matching row, exactly as ADR-C-008 and
adr-c-007.md's handoff note flag. Add the row from the component's
own marker comment.
Also add a small guard to check-tokens.sh (folded into check:tokens,
as ADR-C-008 suggests as an optional step): it diffs the marker set
in code against the register's rows and fails CI on drift. Verified
working with a scratch marker file before removing it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>