feat: add consolidation script (Phase 2) — sleep replay via Hermes cron

[ardhaecosystem]

Summary

Phase 2: the consolidation scheduler — the brain's "sleep replay" cycle. The Hippocampus coordinator already had run_consolidation() and extract_schemas() from Phase 1, but nothing called them. Now there's an entry point.

What Changed

New: scripts/consolidate.py

A standalone script that connects to FalkorDB directly and runs the offline hippocampus batch:

1. Drain online contradictions — contradictions detected during episode ingestion (Phase 1)
2. Offline contradiction detection — cross-episode contradictions over the full graph
3. Hebbian strengthening — co-occurring entity groups
4. Schema extraction (--schemas flag) — neocortical slow learning
5. Pruning candidates (--prune flag) — entities below forgetting curve threshold (report only, does not delete)

Prints a JSON summary to stdout. Exit 0 on success, 1 on error.

Design decision: standalone script, not a daemon

No internal scheduler thread, no second event loop, no daemon. Hermes cron's no-agent mode runs the script on a schedule — that's the "what triggers background work" mechanism. The consolidation_interval_hours config value (default: 6.0) is a recommendation for the cron cadence.

# Via Hermes cron (recommended)
hermes cron create "every 6h" "python /path/to/synapse/scripts/consolidate.py" --no-agent

# Manual
python scripts/consolidate.py --schemas --prune

Skipped: plugin CLI registration (hermes synapse consolidate). Requires plugin directory setup — standalone script works now without it. Add when the plugin directory structure is formalized.

Updated: docs/hippocampus.md

Replaced the "future feature" placeholder with actual usage instructions (cron setup + manual commands + what-it-does table).

Updated: README.md

• Feature checklist: consolidation now ✅ (was ⏳ pending)
• How It Works diagram: "Background (sleep)" now references scripts/consolidate.py (was "Phase 2")
• Project structure: added scripts/consolidate.py
• Roadmap: moved consolidation to Done, removed from In Progress

Test Results

• 118 passed in 0.61s (was 113, +5 new tests)
• ruff check src/ tests/ scripts/ — all checks passed

New tests (test_consolidate.py)

• _age_days with valid timestamp, empty string, invalid timestamp
• Script --help exits 0
• Script exits 1 with JSON error when FalkorDB unavailable