Schema says ids use hyphens and keys use snake_case, but only shows the regex #41

From a peer session's first real run. It cost 22 errors and a wrong fix.

traceos.schema.json requires:

• ids: ^(system|domain|flow|...)\.[a-z0-9-]+(\.[a-z0-9-]+)*$ — hyphens, no underscores
• keys and enum values: snake_case — transitions_to, coverage_declared, user_action

Both are defensible, the combination is not discoverable, and the validator reports the
id rule as a raw regex. The peer read the snake_case keys, applied a blunt
underscore-to-hyphen substitution to fix the ids, and broke the keywords instead.

Fix is a sentence, not a rule change: the id error message should say ids use hyphens and
keys use underscores, and the spec should say it once where ids are introduced.