v2.9.4 — gh_pushed source normalization

Follow-up to v2.9.3 — fix the source, not just the symptom

• Enrichment writers (fast_enrich.py, gemini_utils.py) now store gh_pushed as None when GitHub data is unavailable, instead of the string "N/A" that was reaching datetime.fromisoformat(). gh_license keeps its displayed "N/A" string sentinel.
• agentic_curator.py — hardened the twin fromisoformat() call in the MVQ-penalty check so a bad date value can't crash a curation batch.
• scripts/normalize_gh_pushed.py — one-off migration for the 281 existing gh_pushed: N/A rows (run in CI to avoid SQLite float-serialization churn; see docstring).

Existing N/A values remain tolerated by the v2.9.3 audit until the data is re-enriched.

🤖 Generated with Claude Code