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-codemaps.md

@@ -1,17 +0,0 @@
-# Update Codemaps
-
-Analyze the codebase structure and update architecture documentation:
-
-1. Scan all source files for imports, exports, and dependencies
-2. Generate token-lean codemaps in the following format:
-   - codemaps/architecture.md - Overall architecture
-   - codemaps/backend.md - Backend structure  
-   - codemaps/frontend.md - Frontend structure
-   - codemaps/data.md - Data models and schemas
-
-3. Calculate diff percentage from previous version
-4. If changes > 30%, request user approval before updating
-5. Add freshness timestamp to each codemap
-6. Save reports to .reports/codemap-diff.txt
-
-Use TypeScript/Node.js for analysis. Focus on high-level structure, not implementation details.