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-testing.md

@@ -1,39 +0,0 @@
----
-description: "Python testing: pytest framework, coverage reporting, test categorization with markers"
-globs: ["**/*.py"]
-alwaysApply: false
----
-
-# Python Testing
-
-> This file extends [common/testing.md](../common/testing.md) with Python specific content.
-
-## Framework
-
-Use **pytest** as the testing framework.
-
-## Coverage
-
-```bash
-pytest --cov=src --cov-report=term-missing
-```
-
-## Test Organization
-
-Use `pytest.mark` for test categorization:
-
-```python
-import pytest
-
-@pytest.mark.unit
-def test_calculate_total():
-    ...
-
-@pytest.mark.integration
-def test_database_connection():
-    ...
-```
-
-## Reference
-
-See skill: `python-testing` for detailed pytest patterns and fixtures.