feat: add Cursor IDE support with pre-translated configs

Add complete .cursor/ directory with rules, agents, skills, commands,
and MCP config adapted for Cursor's format. This makes ecc-universal
a truly cross-IDE package supporting Claude Code, Cursor, and OpenCode.

- 27 rule files with YAML frontmatter (description, globs, alwaysApply)
- 13 agent files with full model IDs and readonly flags
- 30 skill directories (identical Agent Skills standard, no translation)
- 31 command files (5 multi-* stubbed for missing codeagent-wrapper)
- MCP config with Cursor env interpolation syntax
- README.md and MIGRATION.md documentation
- install.sh --target cursor flag for project-scoped installation
- package.json updated with .cursor/ in files and cursor keywords

.cursor/rules/python-patterns.md

@@ -0,0 +1,40 @@
+---
+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.