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-coding-style.md

@@ -1,43 +0,0 @@
----
-description: "Python coding style: PEP 8, type annotations, frozen dataclasses, black/isort/ruff formatting"
-globs: ["**/*.py"]
-alwaysApply: false
----
-
-# Python Coding Style
-
-> This file extends [common/coding-style.md](../common/coding-style.md) with Python specific content.
-
-## Standards
-
-- Follow **PEP 8** conventions
-- Use **type annotations** on all function signatures
-
-## Immutability
-
-Prefer immutable data structures:
-
-```python
-from dataclasses import dataclass
-
-@dataclass(frozen=True)
-class User:
-    name: str
-    email: str
-
-from typing import NamedTuple
-
-class Point(NamedTuple):
-    x: float
-    y: float
-```
-
-## Formatting
-
-- **black** for code formatting
-- **isort** for import sorting
-- **ruff** for linting
-
-## Reference
-
-See skill: `python-patterns` for comprehensive Python idioms and patterns.