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/commands/quality-reviewer.md

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+---
+description: Review distilled content quality. Multi-criteria scoring with decision routing (approve/refactor/deep_research/reject).
+argument-hint: <distill-id|all-pending> [--auto-approve] [--threshold 0.85]
+allowed-tools: Read, Write, Bash, Glob, Grep
+---
+
+# Quality Reviewer
+
+Review distilled content for quality and route decisions.
+
+## Arguments
+- `<distill-id|all-pending>`: Specific distill ID or review all pending
+- `--auto-approve`: Auto-approve scores above threshold
+- `--threshold`: Approval threshold (default: 0.85)
+
+## Review Criteria
+
+### Scoring Dimensions
+
+| Criterion | Weight | Checks |
+|-----------|--------|--------|
+| **Accuracy** | 25% | Factual correctness, up-to-date info, proper attribution |
+| **Completeness** | 20% | Covers key concepts, includes examples, addresses edge cases |
+| **Clarity** | 20% | Clear structure, concise language, logical flow |
+| **Prompt Engineering Quality** | 25% | Demonstrates techniques, shows before/after, actionable |
+| **Usability** | 10% | Easy to reference, searchable keywords, appropriate length |
+
+### Score Calculation
+
+```python
+score = (
+    accuracy * 0.25 +
+    completeness * 0.20 +
+    clarity * 0.20 +
+    prompt_eng_quality * 0.25 +
+    usability * 0.10
+)
+```
+
+## Decision Thresholds
+
+| Score | Decision | Action |
+|-------|----------|--------|
+| ≥ 0.85 | **APPROVE** | Ready for export |
+| 0.60-0.84 | **REFACTOR** | Re-distill with feedback |
+| 0.40-0.59 | **DEEP_RESEARCH** | Gather more sources |
+| < 0.40 | **REJECT** | Archive (low quality) |
+
+## Review Process
+
+### 1. Load Distilled Content
+```bash
+source ~/.envrc
+mysql -u $MYSQL_USER -p"$MYSQL_PASSWORD" reference_library -e \
+  "SELECT * FROM distilled_content WHERE distill_id = $ID"
+```
+
+### 2. Evaluate Each Criterion
+
+Score 0.0 to 1.0 for each dimension.
+
+### 3. Generate Assessment
+
+```json
+{
+  "accuracy": 0.90,
+  "completeness": 0.85,
+  "clarity": 0.95,
+  "prompt_engineering_quality": 0.88,
+  "usability": 0.82,
+  "overall_score": 0.88,
+  "decision": "approve",
+  "feedback": "Well-structured with clear examples...",
+  "refactor_instructions": null
+}
+```
+
+### 4. Log Review
+
+```sql
+INSERT INTO review_logs
+  (distill_id, review_round, reviewer_type, quality_score,
+   assessment, decision, feedback, refactor_instructions)
+VALUES
+  (?, 1, 'claude_review', ?, ?, ?, ?, ?);
+```
+
+### 5. Update Status
+
+```sql
+UPDATE distilled_content
+SET review_status = 'approved'
+WHERE distill_id = ?;
+```
+
+## Decision Routing
+
+**APPROVE → markdown-exporter**
+Content is ready for export.
+
+**REFACTOR → content-distiller**
+Re-distill with specific feedback:
+```json
+{"refactor_instructions": "Add more code examples for the API authentication section"}
+```
+
+**DEEP_RESEARCH → web-crawler**
+Need more sources:
+```json
+{"research_queries": ["Claude API authentication examples", "Anthropic SDK best practices"]}
+```
+
+**REJECT → Archive**
+Mark as rejected, optionally note reason.
+
+## Example Usage
+
+```
+/quality-reviewer 15
+/quality-reviewer all-pending --auto-approve
+/quality-reviewer 42 --threshold 0.80
+```