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/shared/config/export_config.yaml

@@ -0,0 +1,46 @@
+# Reference Curator - Export Configuration
+# Location: ~/.config/reference-curator/export_config.yaml
+#
+# Copy this file to ~/.config/reference-curator/export_config.yaml
+
+output:
+  base_path: ~/reference-library/exports/
+
+  # Project files format (for Claude Projects)
+  project_files:
+    structure: nested_by_topic  # flat | nested_by_topic | nested_by_source
+    index_file: INDEX.md
+    include_metadata: true
+    max_file_size_kb: 500
+
+  # Fine-tuning dataset format
+  fine_tuning:
+    format: jsonl
+    include_system_prompt: true
+    system_prompt: "You are an expert on AI and prompt engineering."
+    max_tokens_per_sample: 4096
+
+  # Knowledge base format
+  knowledge_base:
+    structure: flat
+    include_toc: true
+
+# Quality thresholds
+quality:
+  min_score_for_export: 0.80
+  require_human_review: false
+  auto_approve_tier1_sources: true
+  auto_approve_min_score: 0.80
+
+# Cross-reference settings
+cross_references:
+  enabled: true
+  min_concept_overlap: 2
+  max_related_docs: 5
+
+# Verification
+verification:
+  check_broken_links: true
+  validate_markdown: true
+  check_duplicates: true
+  max_allowed_duplicates: 0