Bug: Potential injection via unescaped prompt text in Ralph Wiggum setup heredoc

Description

In plugins/ralph-wiggum/scripts/setup-ralph-loop.sh (lines 140-150), the user-provided prompt text is inserted directly into a markdown file via a heredoc without any escaping:

cat > .claude/ralph-loop.local.md <<EOF
...
$PROMPT
EOF

If the prompt contains the literal string EOF on its own line, or shell-special characters, this could cause:

• Premature heredoc termination, resulting in a truncated or malformed file
• Unexpected shell expansion of variables or commands within the prompt text

Expected Behavior

User-provided prompt text should be safely written to the file without risk of heredoc injection or shell expansion.

Suggested Fix

Use a quoted heredoc delimiter to prevent shell expansion, or write the file using printf or a similar method that does not interpret the content.