Ralph Loop plugin: stop-hook.sh fails on Windows - cat command not found

Question

## Bug Description

The Ralph Loop plugin's stop-hook.sh fails on Windows with Git Bash because the cat command is not found in PATH when the hook executes.

## Error Message

```
Stop hook error: Failed with non-blocking status code:
  hooks/stop-hook.sh: line 10: cat: command not found
```

## Root Cause

Line 10 uses `HOOK_INPUT=$(cat)` but PATH doesn't include /usr/bin on Windows.

## Suggested Fix

Use full path: `HOOK_INPUT=$("/usr/bin/cat")`