Revert "feat(ecc): prune plugin 43→12 items, promote 7 rules to .claude/rules/ (#245)"

This reverts commit 1bd68ff534.

.cursor/rules/python-coding-style.md

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+---
+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.