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/04-content-distiller/code/CLAUDE.md

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+# Content Distiller
+
+Analyzes and distills raw crawled content into concise reference materials. Extracts key concepts, code snippets, and creates structured summaries.
+
+## Trigger Keywords
+"distill content", "summarize document", "extract key concepts", "process raw content", "create reference summary"
+
+## Goals
+
+1. **Compress** - Reduce token count while preserving essential information
+2. **Structure** - Organize content for easy retrieval
+3. **Extract** - Pull out code snippets, key concepts, patterns
+4. **Annotate** - Add metadata for searchability
+
+## Workflow
+
+### Step 1: Load Raw Content
+```bash
+python scripts/load_pending.py --output pending_docs.json
+```
+
+### Step 2: Analyze Content Structure
+Identify document characteristics:
+- Has code blocks?
+- Has headers?
+- Has tables?
+- Estimated tokens?
+
+### Step 3: Extract Key Components
+```bash
+python scripts/extract_components.py --doc-id 123 --output components.json
+```
+
+Extracts:
+- Code snippets with language tags
+- Key concepts and definitions
+- Best practices
+- Techniques and patterns
+
+### Step 4: Create Structured Summary
+Output template:
+```markdown
+# {title}
+
+**Source:** {url}
+**Type:** {source_type} | **Tier:** {credibility_tier}
+**Distilled:** {date}
+
+## Executive Summary
+{2-3 sentence overview}
+
+## Key Concepts
+{bulleted list with definitions}
+
+## Techniques & Patterns
+{extracted techniques with use cases}
+
+## Code Examples
+{relevant code snippets}
+
+## Best Practices
+{actionable recommendations}
+```
+
+### Step 5: Optimize for Tokens
+Target: 25-35% of original token count
+```bash
+python scripts/optimize_content.py --doc-id 123 --target-ratio 0.30
+```
+
+### Step 6: Store Distilled Content
+```bash
+python scripts/store_distilled.py --doc-id 123 --content distilled.md
+```
+
+## Quality Metrics
+
+| Metric | Target |
+|--------|--------|
+| Compression Ratio | 25-35% of original |
+| Key Concept Coverage | ≥90% of important terms |
+| Code Snippet Retention | 100% of relevant examples |
+| Readability | Clear, scannable structure |
+
+## Handling Refactor Requests
+
+When `quality-reviewer` returns `refactor`:
+```bash
+python scripts/refactor_content.py --distill-id 456 --instructions "Add more examples"
+```
+
+## Scripts
+
+- `scripts/load_pending.py` - Load documents pending distillation
+- `scripts/extract_components.py` - Extract code, concepts, patterns
+- `scripts/optimize_content.py` - Token optimization
+- `scripts/store_distilled.py` - Save to database
+- `scripts/refactor_content.py` - Handle refactor requests
+
+## Integration
+
+| From | To |
+|------|-----|
+| content-repository | Raw document records |
+| → | quality-reviewer (distilled content) |
+| quality-reviewer | Refactor instructions (loop back) |