Add documentation for using uv scripts in hack directory

hack/CLAUDE.md

@@ -0,0 +1,17 @@
+# Hack Directory Guidelines
+
+## Using UV Scripts for One-Off Tools
+
+When creating standalone Python scripts in this directory, use uv's inline script dependencies:
+
+```python
+#!/usr/bin/env -S uv run
+# /// script
+# dependencies = [
+#     "pillow",
+#     "requests",
+# ]
+# ///
+```
+
+This allows scripts to be self-contained with their dependencies and run with `uv run script.py` without manual environment setup. UV will automatically create an isolated environment and install the required packages on first run.