[codex] fix: harden secret ingestion and query memory

[aa-matsunari]

Summary

• redact credential-like values before persisting query memory
• skip files with inline secret content during detect()

Changed files

• graphify/detect.py
• graphify/ingest.py
• tests/test_detect.py
• tests/test_ingest.py

Impact

• prevents API keys and other secrets from being re-ingested into future graph runs

Tests

• /tmp/graphify-review/.venv/bin/python -m pytest /tmp/graphify-review/tests/test_detect.py /tmp/graphify-review/tests/test_ingest.py