docs: document the approved ontology record format

[kms970]

Goal

Document the shape of approved ontology records in a compact schema reference.

Suggested scope

• Add a new docs page, for example docs/ONTOLOGY_FORMAT.md.
• Explain common fields in ontology.jsonl using synthetic examples.
• Clarify the difference between raw conversation input, pending candidates, approved records, and compiled output.
• Link the page from README.md and/or docs/AI_QUICKSTART.md.

Acceptance criteria

• Examples are synthetic and public-safe.
• The page explains why raw/conversations/ and review/*.jsonl should not be committed.
• The page includes at least one valid example record.
• python3 -m pytest -q still passes.

Notes

This should be a docs-only contribution unless the current format is unclear enough that tests need to be added.