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/rules/common-performance.md

@@ -1,60 +0,0 @@
----
-description: "Performance optimization: model selection strategy, context window management, extended thinking"
-alwaysApply: true
----
-
-# Performance Optimization
-
-## Model Selection Strategy
-
-**Haiku 4.5** (90% of Sonnet capability, 3x cost savings):
-- Lightweight agents with frequent invocation
-- Pair programming and code generation
-- Worker agents in multi-agent systems
-
-**Sonnet 4.5** (Best coding model):
-- Main development work
-- Orchestrating multi-agent workflows
-- Complex coding tasks
-
-**Opus 4.5** (Deepest reasoning):
-- Complex architectural decisions
-- Maximum reasoning requirements
-- Research and analysis tasks
-
-## Context Window Management
-
-Avoid last 20% of context window for:
-- Large-scale refactoring
-- Feature implementation spanning multiple files
-- Debugging complex interactions
-
-Lower context sensitivity tasks:
-- Single-file edits
-- Independent utility creation
-- Documentation updates
-- Simple bug fixes
-
-## Extended Thinking + Plan Mode
-
-Extended thinking is enabled by default, reserving up to 31,999 tokens for internal reasoning.
-
-Control extended thinking via:
-- **Toggle**: Option+T (macOS) / Alt+T (Windows/Linux)
-- **Config**: Set `alwaysThinkingEnabled` in `~/.claude/settings.json`
-- **Budget cap**: `export MAX_THINKING_TOKENS=10000`
-- **Verbose mode**: Ctrl+O to see thinking output
-
-For complex tasks requiring deep reasoning:
-1. Ensure extended thinking is enabled (on by default)
-2. Enable **Plan Mode** for structured approach
-3. Use multiple critique rounds for thorough analysis
-4. Use split role sub-agents for diverse perspectives
-
-## Build Troubleshooting
-
-If build fails:
-1. Use **build-error-resolver** agent
-2. Analyze error messages
-3. Fix incrementally
-4. Verify after each fix