feat(ecc): prune plugin 43→12 items, promote 7 rules to .claude/rules/ (#245)

ECC community plugin pruning: removed 530+ non-essential files
(.cursor/, .opencode/, docs/ja-JP, docs/zh-CN, docs/zh-TW,
language-specific skills/agents/rules). Retained 4 agents,
3 commands, 5 skills. Promoted 13 rule files (8 common + 5
typescript) to .claude/rules/ for CC native loading. Extracted
reusable patterns to EXTRACTED-PATTERNS.md.

.cursor/commands/update-docs.md

@@ -1,31 +0,0 @@
-# Update Documentation
-
-Sync documentation from source-of-truth:
-
-1. Read package.json scripts section
-   - Generate scripts reference table
-   - Include descriptions from comments
-
-2. Read .env.example
-   - Extract all environment variables
-   - Document purpose and format
-
-3. Generate docs/CONTRIB.md with:
-   - Development workflow
-   - Available scripts
-   - Environment setup
-   - Testing procedures
-
-4. Generate docs/RUNBOOK.md with:
-   - Deployment procedures
-   - Monitoring and alerts
-   - Common issues and fixes
-   - Rollback procedures
-
-5. Identify obsolete documentation:
-   - Find docs not modified in 90+ days
-   - List for manual review
-
-6. Show diff summary
-
-Single source of truth: package.json and .env.example