feat: measurer.py — compounding intelligence metrics engine

Implements issue #14: 7 metrics that prove knowledge compounding.

Metrics:
- Knowledge velocity: new facts/day (from index.json)
- Knowledge coverage: % domains with 10+ facts (from YAML files)
- Hit rate: % sessions referencing bootstrap knowledge
- Error recurrence: same errors across sessions (should decrease)
- Task completion: % sessions with successful end_reason
- First-try success: actions without backtracking (tool/msg ratio)
- Knowledge age: staleness of facts (freshness score)

Data sources:
- knowledge/index.json + YAML files for fact metrics
- ~/.hermes/state.db sessions + messages tables

Features:
- JSON and markdown output formats
- --since, --repo, --format flags
- 7-day trend tracking via snapshot persistence
- Runs in 33ms on 11.9K sessions / 192K messages
- Dashboard auto-generation with --save-snapshot

Closes #14

scripts/validate_knowledge.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""
+Validate knowledge files and index.json against the schema.
+
+Usage:
+    python scripts/validate_knowledge.py
+"""
+
+import json
+import sys
+from pathlib import Path
+
+VALID_CATEGORIES = {"fact", "pitfall", "pattern", "tool-quirk", "question"}
+REQUIRED_FACT_FIELDS = {"id", "fact", "category", "domain", "confidence"}
+MAX_FACT_LENGTH = 280
+
+
+def validate_fact(fact, source=""):
+    errors = []
+    for field in REQUIRED_FACT_FIELDS:
+        if field not in fact:
+            errors.append(f"{source}: missing required field '{field}'")
+    if "fact" in fact:
+        if not isinstance(fact["fact"], str) or len(fact["fact"].strip()) == 0:
+            errors.append(f"{source}: 'fact' must be non-empty string")
+        elif len(fact["fact"]) > MAX_FACT_LENGTH:
+            errors.append(f"{source}: 'fact' exceeds {MAX_FACT_LENGTH} chars")
+    if "category" in fact and fact["category"] not in VALID_CATEGORIES:
+        errors.append(f"{source}: invalid category '{fact['category']}'")
+    if "confidence" in fact:
+        if not isinstance(fact["confidence"], (int, float)):
+            errors.append(f"{source}: 'confidence' must be a number")
+        elif not (0.0 <= fact["confidence"] <= 1.0):
+            errors.append(f"{source}: 'confidence' must be 0.0-1.0")
+    if "id" in fact:
+        parts = fact["id"].split(":")
+        if len(parts) != 3:
+            errors.append(f"{source}: 'id' must be domain:category:sequence")
+        elif parts[1] not in VALID_CATEGORIES:
+            errors.append(f"{source}: id category '{parts[1]}' invalid")
+    return errors
+
+
+def main():
+    repo_root = Path(__file__).parent.parent
+    index_path = repo_root / "knowledge" / "index.json"
+    all_errors = []
+
+    if not index_path.exists():
+        print(f"VALIDATION FAILED: index.json not found at {index_path}")
+        sys.exit(1)
+
+    with open(index_path) as f:
+        data = json.load(f)
+
+    if "version" not in data:
+        all_errors.append("index.json: missing 'version'")
+    if "facts" not in data or not isinstance(data["facts"], list):
+        all_errors.append("index.json: missing or invalid 'facts'")
+
+    seen_ids = set()
+    for i, fact in enumerate(data.get("facts", [])):
+        all_errors.extend(validate_fact(fact, f"facts[{i}]"))
+        if "id" in fact:
+            if fact["id"] in seen_ids:
+                all_errors.append(f"index.json: duplicate id '{fact['id']}'")
+            seen_ids.add(fact["id"])
+
+    if all_errors:
+        print(f"VALIDATION FAILED - {len(all_errors)} error(s):\n")
+        for e in all_errors:
+            print(f"  x {e}")
+        sys.exit(1)
+    else:
+        print(f"VALIDATION PASSED - {len(data.get('facts', []))} facts, schema v{data.get('version', '?')}")
+        sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()