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-security.md

@@ -1,31 +0,0 @@
----
-description: "Python security: dotenv secret management, bandit static analysis"
-globs: ["**/*.py"]
-alwaysApply: false
----
-
-# Python Security
-
-> This file extends [common/security.md](../common/security.md) with Python specific content.
-
-## Secret Management
-
-```python
-import os
-from dotenv import load_dotenv
-
-load_dotenv()
-
-api_key = os.environ["OPENAI_API_KEY"]  # Raises KeyError if missing
-```
-
-## Security Scanning
-
-- Use **bandit** for static security analysis:
-  ```bash
-  bandit -r src/
-  ```
-
-## Reference
-
-See skill: `django-security` for Django-specific security guidelines (if applicable).