address review: remove .cursor/ duplicate, use is not None checks

Changes based on CodeRabbit review feedback:

1. Remove entire .cursor/ directory — it was an identical copy of the
   main skills/commands/agents/rules, causing maintenance drift.
   Users of Cursor can reference the canonical files directly.

2. Use explicit `is not None` checks instead of truthiness for
   parsed['input'] and parsed['output']. Empty strings or empty
   dicts are valid values that should be preserved.

.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.