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.

.opencode/commands/update-docs.md

@@ -1,67 +0,0 @@
----
-description: Update documentation for recent changes
-agent: doc-updater
-subtask: true
----
-
-# Update Docs Command
-
-Update documentation to reflect recent changes: $ARGUMENTS
-
-## Your Task
-
-1. **Identify changed code** - `git diff --name-only`
-2. **Find related docs** - README, API docs, guides
-3. **Update documentation** - Keep in sync with code
-4. **Verify accuracy** - Docs match implementation
-
-## Documentation Types
-
-### README.md
-- Installation instructions
-- Quick start guide
-- Feature overview
-- Configuration options
-
-### API Documentation
-- Endpoint descriptions
-- Request/response formats
-- Authentication details
-- Error codes
-
-### Code Comments
-- JSDoc for public APIs
-- Complex logic explanations
-- TODO/FIXME cleanup
-
-### Guides
-- How-to tutorials
-- Architecture decisions (ADRs)
-- Troubleshooting guides
-
-## Update Checklist
-
-- [ ] README reflects current features
-- [ ] API docs match endpoints
-- [ ] JSDoc updated for changed functions
-- [ ] Examples are working
-- [ ] Links are valid
-- [ ] Version numbers updated
-
-## Documentation Quality
-
-### Good Documentation
-- Accurate and up-to-date
-- Clear and concise
-- Has working examples
-- Covers edge cases
-
-### Avoid
-- Outdated information
-- Missing parameters
-- Broken examples
-- Ambiguous language
-
----
-
-**IMPORTANT**: Documentation should be updated alongside code changes, not as an afterthought.