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/build-fix.md

@@ -1,29 +0,0 @@
-# Build and Fix
-
-Incrementally fix TypeScript and build errors:
-
-1. Run build: npm run build or pnpm build
-
-2. Parse error output:
-   - Group by file
-   - Sort by severity
-
-3. For each error:
-   - Show error context (5 lines before/after)
-   - Explain the issue
-   - Propose fix
-   - Apply fix
-   - Re-run build
-   - Verify error resolved
-
-4. Stop if:
-   - Fix introduces new errors
-   - Same error persists after 3 attempts
-   - User requests pause
-
-5. Show summary:
-   - Errors fixed
-   - Errors remaining
-   - New errors introduced
-
-Fix one error at a time for safety!