Update dummyVariable naming schema across branches

[DougManuel]

Summary

The dummyVariable naming convention in metadata_registry.yaml and variable_details.yaml has been updated on the diet-score branch to match actual practice. The old schema allowed patterns that are no longer correct.

Changes made (diet-score branch)

inst/metadata/documentation/metadata_registry.yaml:

• Old regex: ^[a-zA-Z0-9_]+_(cat|cont)[0-9]+(_[0-9]+|_NA::[a-z])?$
• New categorical regex: ^[a-zA-Z0-9_]+_cat[0-9]+(_[0-9]+|_NA[a-z])$
• Continuous/Func rows: N/A
• Added missing_categories examples (_NAa, _NAb)
• Removed _cont{N} examples (not used in practice)

inst/metadata/schemas/core/variable_details.yaml:

• Updated dummyVariable notes to match new convention
• Removed _cont{N} examples
• Added _NAa/_NAb examples

What changed

1. No colons — _NAa and _NAb instead of _NA::a and _NA::b
2. No _cont pattern — continuous variables use N/A
3. Func rows use N/A — not a constructed name

Propagation needed

These schema files exist on multiple branches under review. The updated schema needs to be propagated to:

• v3-smoking (smoking harmonization)
• main (after current PRs merge)
• Any other active feature branches

The cchsflow-review SKILL.md (Check 5b) enforces the correct convention regardless of which schema version is on the branch, so this is not blocking reviews.

Related

• PR diet score #148 (diet variables) — where the discrepancy was discovered
• cchsflow-review SKILL.md Check 5b documents the convention