In .github/workflows/agentready-assessment.yml, lines 51-78, modify the "Comment on PR" step's script to find and update an existing comment instead of always creating a new one. The approach:

1. Add a marker string like `<!-- agentready-assessment -->` to the comment body.
2. Before creating a comment, list existing comments on the PR using `github.rest.issues.listComments()` and search for one containing the marker.
3. If found, use `github.rest.issues.updateComment({ comment_id: existingComment.id, ... })` to update it.
4. If not found, use `github.rest.issues.createComment()` to create a new one.

Example pattern:

const marker = '<!-- agentready-assessment -->';
const body = marker + '\n' + report;
const { data: comments } = await github.rest.issues.listComments({
  issue_number: context.issue.number,
  owner: context.repo.owner,
  repo: context.repo.repo,
});
const existing = comments.find(c => c.body && c.body.includes(marker));
if (existing) {
  await github.rest.issues.updateComment({
    comment_id: existing.id,
    owner: context.repo.owner,
    repo: context.repo.repo,
    body: body,
  });
} else {
  await github.rest.issues.createComment({
    issue_number: context.issue.number,
    owner: context.repo.owner,
    repo: context.repo.repo,
    body: body,
  });
}