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/context-research.md

@@ -1,31 +0,0 @@
----
-description: "Research context: exploration mode with understanding-before-acting approach"
-alwaysApply: false
----
-
-# Research Context
-
-Mode: Exploration, investigation, learning
-Focus: Understanding before acting
-
-## Behavior
-- Read widely before concluding
-- Ask clarifying questions
-- Document findings as you go
-- Don't write code until understanding is clear
-
-## Research Process
-1. Understand the question
-2. Explore relevant code/docs
-3. Form hypothesis
-4. Verify with evidence
-5. Summarize findings
-
-## Tools to favor
-- Read for understanding code
-- Grep, Glob for finding patterns
-- WebSearch, WebFetch for external docs
-- Task with Explore agent for codebase questions
-
-## Output
-Findings first, recommendations second