docs(shared): add the missing language-switcher row to the CIBG gap register (RB-32)

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>

libs/shared/docs/cibg-gaps.mdx

@@ -31,6 +31,7 @@ placed above the `@Component` decorator, plus `parameters: { cibgGap: true }` an
 | `debug-state`                           | n/a                  | Dev-only tool, deliberately off-theme — see the component's own `ponytail:` note.                                                                      |
 | `status-badge`                          | n/a                  | Deliberate custom status dot, not Bootstrap's `.badge` (pill padding/colour don't fit).                                                                |
 | `placeholder-chip`                      | n/a                  | No vendored inline-chip/tag class.                                                                                                                     |
+| `language-switcher`                     | Taal instellen       | No vendored Huisstijl class ships for it; a small hand-rolled surface built from the token bridge.                                                     |
 
 Not a gap: `confirmation` renders entirely with vendored `.confirmation*` classes (no `styles:
 [...]` block) — its header comment names the pattern, no marker needed. The `upload/` suite