feat: add automated PR review agent that summarizes changes as a comment

[Copilot]

No automated PR summarization existed — reviewers had to manually parse diffs to understand scope and risk.

What's added

.github/workflows/pr-review-agent.yml — GitHub Actions workflow that fires on every PR open/update and posts an AI-generated summary comment.

Behavior

• Fetches PR metadata + up to 100 changed files with diff patches via GitHub REST API
• Sends a structured prompt (title, description, file list, first 15 patches ≤ 2 000 chars each) to GitHub Models (gpt-4o-mini)
• Posts a comment structured as Summary / Changes / Potential concerns
• Deletes the previous bot comment before posting — re-pushes always show one up-to-date summary
• Falls back to a plain file-change list if the Models endpoint is unavailable

Permissions

permissions:
  contents: read
  pull-requests: write

Token note

GITHUB_TOKEN works for GitHub Models on public repos. For private repos, a PAT with models:read scope stored as a repository secret is required — swap it into the env.GITHUB_TOKEN field.

Original prompt

create PR review agent for this repo, so when there is a PR made, summarizes the chnages and add as a comment to PR

The user has attached the following file paths as relevant context:

• .github/copilot-instructions.md

Created from VS Code.

[github-actions]

🤖 PR Review Agent

Summary

This PR — feat: add automated PR review agent that summarizes changes as a comment — modifies 1 file(s).

Changes

• .github/workflows/pr-review-agent.yml (added): +140 −0

Potential concerns

AI summarization was unavailable; please review manually.

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Generated automatically by the PR Review Agent.