Generate a GitHub pull request title and description for this completed task.

Task prompt:
{task_prompt}

Commits on branch:
{commit_log}

Files changed:
{diff_stat}

Format your response EXACTLY like this (no markdown code fences):
TITLE: <concise PR title, max 72 chars>

BODY:
## Summary
<2-3 sentences describing what was done and why>

## Changes
<bullet points of key changes>

Output ONLY in the format above, nothing else.