feat(reference-curator): Add portable skill suite for reference documentation curation

6 modular skills for curating, processing, and exporting reference docs:
- reference-discovery: Search and validate authoritative sources
- web-crawler-orchestrator: Multi-backend crawling (Firecrawl/Node/aiohttp/Scrapy)
- content-repository: MySQL storage with version tracking
- content-distiller: Summarization and key concept extraction
- quality-reviewer: QA loop with approve/refactor/research routing
- markdown-exporter: Structured output for Claude Projects or fine-tuning

Cross-machine installation support:
- Environment-based config (~/.reference-curator.env)
- Commands tracked in repo, symlinked during install
- install.sh with --minimal, --check, --uninstall modes
- Firecrawl MCP as default (always available)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

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+# Content Repository
+
+MySQL storage management for the reference library. Handles document storage, version control, deduplication, and retrieval.
+
+## 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
+
+## Database Setup
+
+```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" \
+  --url "https://docs.anthropic.com/..." \
+  --doc-type webpage \
+  --raw-path ~/reference-library/raw/2025/01/abc123.md
+```
+
+### Check Duplicate
+```bash
+python scripts/check_duplicate.py --url "https://docs.anthropic.com/..."
+```
+
+### Query by Topic
+```bash
+python scripts/query_topic.py --topic-slug prompt-engineering --min-quality 0.80
+```
+
+## Table Quick Reference
+
+| Table | Purpose | Key Fields |
+|-------|---------|------------|
+| `sources` | Authorized sources | source_type, credibility_tier, vendor |
+| `documents` | Document metadata | url_hash (dedup), version, crawl_status |
+| `distilled_content` | Processed summaries | review_status, compression_ratio |
+| `review_logs` | QA decisions | quality_score, decision |
+| `topics` | Taxonomy | topic_slug, parent_topic_id |
+| `document_topics` | Many-to-many links | relevance_score |
+| `export_jobs` | Export tracking | export_type, status |
+
+## Status Values
+
+**crawl_status:** `pending` → `completed` | `failed` | `stale`
+
+**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
+
+## Integration
+
+| From | Action | To |
+|------|--------|-----|
+| crawler-orchestrator | Store crawled content | → |
+| → | Query pending docs | content-distiller |
+| quality-reviewer | Update review_status | → |
+| → | Query approved content | markdown-exporter |