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

@@ -1,44 +1,58 @@
 # Content Distiller
 
-Analyzes and distills raw crawled content into concise reference materials. Extracts key concepts, code snippets, and creates structured summaries.
+Analyzes and distills raw crawled content into concise reference materials. Claude performs the actual distillation (summarization, key concept extraction). Scripts handle data loading and storage.
 
 ## 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
+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
+### Step 1: Load Pending Documents
 ```bash
-python scripts/load_pending.py --output pending_docs.json
+uv run python scripts/distiller.py load-pending --output pending.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
+### Step 2: Analyze and Distill (Claude)
+For each pending document, Claude reads the raw content and creates:
+- Executive summary (2-3 sentences)
+- Key concepts with definitions
 - Techniques and patterns
+- Code examples
+- Best practices
+
+### Step 3: Store Distilled Content
+```bash
+uv run python scripts/distiller.py store \
+  --doc-id 123 \
+  --content distilled.md \
+  --summary summary.txt \
+  --concepts concepts.json \
+  --snippets snippets.json \
+  --model claude-opus-4-6
+```
+
+### Step 4: Handle Refactor Requests
+When quality-reviewer returns `refactor`, load context for re-distillation:
+```bash
+uv run python scripts/distiller.py refactor --distill-id 456 --output context.json
+```
+
+This outputs a context bundle with the current distilled content, raw source, and all review feedback.
+
+### Step 5: View Distilled Content
+```bash
+uv run python scripts/distiller.py show --distill-id 456
+```
+
+## Distilled Output Template
 
-### Step 4: Create Structured Summary
-Output template:
 ```markdown
 # {title}
 
@@ -62,17 +76,6 @@ Output template:
 {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 |
@@ -82,20 +85,14 @@ python scripts/store_distilled.py --doc-id 123 --content distilled.md
 | 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
+| Command | Purpose |
+|---------|---------|
+| `distiller.py load-pending` | Load documents pending distillation |
+| `distiller.py store` | Save distilled content to DB |
+| `distiller.py refactor` | Load context for re-distillation |
+| `distiller.py show` | Show distilled content details |
 
 ## Integration