Adapt OKF v0.2 semantics into SQLite for Mantis reference harness and advise.py

- Add okf_concepts table to reference/core/database.py with schema version 3.
- Implement OKF v0.2 YAML frontmatter parser and trust tier resolver per spec §5.3.
- Add bi-directional OKF directory bundle export and import (export_okf_bundle / import_okf_bundle).
- Enhance query_security_guidance and scripts/advise.py to provide scoped threat context, trust badges, and few-shot verified patch diffs.
- Support exact resource matching without SQL LIKE wildcard collisions.
- Add --export-okf and --import-okf CLI options to scripts/advise.py.
- Explicitly declare pyyaml in reference/requirements.in.
- Add comprehensive test cases in reference/test_suite.py covering OKF parsing, trust tier derivation, auto-indexing, diff preservation, exact matching, and CLI execution.

TAG=agy
CONV=4edb1ebc-44f1-4bb8-8c17-1b4297c4be13

Change-Id: Idc30a8ab78bb6288820c254f17bf4e2d46f69f07

Author: nickg-ca