Fix pi-review.sh commit message to pass gitlint

gitlint rejected the commit because the Task-Id trailer was treated as a too-short body line.

Problem

Current format:

Namespace: Title

Task-Id: t-123

gitlint sees 'Task-Id: t-123' as a body line and complains it's <20 chars.

Solution

Add a proper body message:

Namespace: Title

Automated commit via pi-review.

Task-Id: t-123

Or construct body from task description (first line/sentence).

Implementation

Update the git commit command to include a body:

git commit -m "$COMMIT_PREFIX: $TITLE" -m "Automated via pi-review." --trailer "Task-Id: $TASK_ID"