feat(reference-curator): implement Python scripts + Gemini quality gate

Build the refcurator shared Python package and 7 CLI scripts that were
previously specification-only. Add Gemini CLI as an independent pre-distillation
quality evaluator, replacing the circular Claude-self-review pattern.

Key changes:
- shared/lib/src/refcurator/: 7-module package (config, db, models, utils,
  manifest, gemini) with PyMySQL + JSON file dual backend
- 7 Click CLI scripts: discover, crawl_mgr, repo, distiller, reviewer,
  exporter, pipeline — each with subcommands for data management
- Gemini quality gate: evaluates raw content BEFORE distillation using
  5 criteria (relevance, authority, completeness, freshness, distill_value)
- Pipeline reordered: discovery → crawl → store → evaluate → distill → export
- Bug fixes from Codex adversarial review:
  - FileBackend now hard-fails on JOIN/aggregate/GROUP BY queries
  - Exporter uses MAX(review_id) to prevent shipping stale approvals
  - Distiller updates existing rows on refactor instead of forking
- Updated all 7 CLAUDE.md directives with real script references
- install.sh updated with refcurator package install step

51/51 E2E tests passing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

custom-skills/90-reference-curator/03-content-repository/code/CLAUDE.md

@@ -1,46 +1,42 @@
 # Content Repository
 
-MySQL storage management for the reference library. Handles document storage, version control, deduplication, and retrieval.
+MySQL storage management for the reference library. Handles document storage, version control, deduplication, and retrieval. Supports MySQL primary backend with JSON file fallback.
 
 ## Trigger Keywords
 "store content", "save to database", "check duplicates", "version tracking", "document retrieval", "reference library DB"
 
 ## Prerequisites
 
-- MySQL 8.0+ with utf8mb4 charset
-- Config file at `~/.config/reference-curator/db_config.yaml`
-- Database `reference_library` initialized
+- `refcurator` package installed (`uv pip install -e shared/lib/`)
+- MySQL 8.0+ (optional — falls back to JSON file storage)
+- Config at `~/.config/reference-curator/db_config.yaml` (optional)
 
-## Database Setup
+## Quick Start
 
 ```bash
-# Initialize database
-mysql -u root -p < references/schema.sql
-
-# Verify tables
-mysql -u root -p reference_library -e "SHOW TABLES;"
-```
-
-## Core Scripts
-
-### Store Document
-```bash
-python scripts/store_document.py \
-  --source-id 1 \
-  --title "Prompt Engineering Guide" \
+# Store a document
+uv run python scripts/repo.py store \
+  --source-id 1 --title "Prompt Engineering Guide" \
   --url "https://docs.anthropic.com/..." \
-  --doc-type webpage \
-  --raw-path ~/reference-library/raw/2025/01/abc123.md
-```
+  --doc-type webpage --raw-path ~/reference-library/raw/abc123.md
 
-### Check Duplicate
-```bash
-python scripts/check_duplicate.py --url "https://docs.anthropic.com/..."
-```
+# Check for duplicates
+uv run python scripts/repo.py check-dup --url "https://docs.anthropic.com/..."
 
-### Query by Topic
-```bash
-python scripts/query_topic.py --topic-slug prompt-engineering --min-quality 0.80
+# Query by topic
+uv run python scripts/repo.py query-topic --topic-slug prompt-engineering --min-quality 0.80
+
+# Get repository stats
+uv run python scripts/repo.py stats
+
+# Find stale documents (older than 30 days)
+uv run python scripts/repo.py find-stale --days 30
+
+# Get pending reviews
+uv run python scripts/repo.py pending-reviews --output pending.json
+
+# Get export-ready content
+uv run python scripts/repo.py export-ready --min-score 0.85
 ```
 
 ## Table Quick Reference
@@ -61,31 +57,17 @@ python scripts/query_topic.py --topic-slug prompt-engineering --min-quality 0.80
 
 **review_status:** `pending` → `in_review` → `approved` | `needs_refactor` | `rejected`
 
-## Common Queries
-
-### Find Stale Documents
-```bash
-python scripts/find_stale.py --output stale_docs.json
-```
-
-### Get Pending Reviews
-```bash
-python scripts/pending_reviews.py --output pending.json
-```
-
-### Export-Ready Content
-```bash
-python scripts/export_ready.py --min-score 0.85 --output ready.json
-```
-
 ## Scripts
 
-- `scripts/store_document.py` - Store new document
-- `scripts/check_duplicate.py` - URL deduplication
-- `scripts/query_topic.py` - Query by topic
-- `scripts/find_stale.py` - Find stale documents
-- `scripts/pending_reviews.py` - Get pending reviews
-- `scripts/db_utils.py` - Database connection utilities
+| Command | Purpose |
+|---------|---------|
+| `repo.py store` | Store a new document |
+| `repo.py check-dup` | URL deduplication check |
+| `repo.py query-topic` | Query documents by topic |
+| `repo.py find-stale` | Find stale documents |
+| `repo.py pending-reviews` | Get pending reviews |
+| `repo.py export-ready` | Get approved content ready for export |
+| `repo.py stats` | Show repository statistics |
 
 ## Integration