feat(curation): data quality pipeline — Phases 1-3

Add comprehensive data curation system to clean up the 197K skill
dataset and show only quality browse-ready skills to users.

Phase 1 — Database exploration:
- Explore scripts (explore.ts, explore.mjs, explore.sql) for analysis
- Discovered: 69% duplicates, 77% aggregator/fork noise

Phase 2 — Data cleanup and classification:
- Schema: 6 new curation columns + 4 indexes
- curate.mjs: 8-step pipeline (classify, dedup, fork detection, etc.)
- Result: 197K → 60K unique → 16K browse-ready skills
- Bug fix: securityStatus was computed but never stored during crawl

Phase 3 — UI browse-ready filters:
- browseReadyFilter applied to 17+ query functions
- Homepage stats show accurate browse-ready counts
- Stats API filtered (previously had no WHERE clause)
- Category counts recalculated (e.g. 45K → 3.1K)
- Featured skills exclude duplicates and aggregators

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/init-db.sql

@@ -348,6 +348,7 @@ BEGIN
     -- Excluded: cached_files (download cache, not content change)
     -- Excluded: indexed_at, last_scanned (indexer bookkeeping)
     -- Excluded: github_stars, github_forks (popularity metrics, not content)
+    -- Excluded: quality_score, quality_details, skill_type, is_duplicate, canonical_skill_id, repo_skill_count (curation metadata)
     IF ROW(NEW.name, NEW.description, NEW.github_owner, NEW.github_repo, NEW.skill_path,
            NEW.branch, NEW.commit_sha, NEW.source_format, NEW.version, NEW.license, NEW.author, NEW.homepage,
            NEW.compatibility, NEW.triggers,
@@ -461,6 +462,19 @@ CREATE INDEX IF NOT EXISTS idx_skills_source_format ON skills(source_format);
 ALTER TABLE skills ADD COLUMN IF NOT EXISTS last_downloaded_at TIMESTAMP WITH TIME ZONE;
 CREATE INDEX IF NOT EXISTS idx_skills_last_downloaded ON skills(last_downloaded_at DESC NULLS LAST);
 
+-- Curation columns (Phase 2 - February 2026)
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS quality_score INTEGER;
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS quality_details JSONB;
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS skill_type TEXT;  -- 'standalone', 'project-bound', 'collection', 'aggregator'
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS is_duplicate BOOLEAN DEFAULT FALSE;
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS canonical_skill_id TEXT;  -- points to original if duplicate
+ALTER TABLE skills ADD COLUMN IF NOT EXISTS repo_skill_count INTEGER;  -- cached count of skills in repo
+
+CREATE INDEX IF NOT EXISTS idx_skills_quality ON skills(quality_score DESC NULLS LAST);
+CREATE INDEX IF NOT EXISTS idx_skills_type ON skills(skill_type);
+CREATE INDEX IF NOT EXISTS idx_skills_duplicate ON skills(is_duplicate);
+CREATE INDEX IF NOT EXISTS idx_skills_content_hash ON skills(content_hash);
+
 -- Grant permissions
 GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO postgres;
 GRANT ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA public TO postgres;