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/python-patterns.md

@@ -1,40 +0,0 @@
----
-description: "Python patterns: Protocol for duck typing, dataclass DTOs, context managers, generators"
-globs: ["**/*.py"]
-alwaysApply: false
----
-
-# Python Patterns
-
-> This file extends [common/patterns.md](../common/patterns.md) with Python specific content.
-
-## Protocol (Duck Typing)
-
-```python
-from typing import Protocol
-
-class Repository(Protocol):
-    def find_by_id(self, id: str) -> dict | None: ...
-    def save(self, entity: dict) -> dict: ...
-```
-
-## Dataclasses as DTOs
-
-```python
-from dataclasses import dataclass
-
-@dataclass
-class CreateUserRequest:
-    name: str
-    email: str
-    age: int | None = None
-```
-
-## Context Managers & Generators
-
-- Use context managers (`with` statement) for resource management
-- Use generators for lazy evaluation and memory-efficient iteration
-
-## Reference
-
-See skill: `python-patterns` for comprehensive patterns including decorators, concurrency, and package organization.