Add PR reviewer TaskSpawner for automated code review

[axon-agent]

Summary

• Add self-development/axon-pr-reviewer.yaml — a new TaskSpawner that automatically reviews pull requests, directly addressing Replace cubic-dev-ai app #408 (replacing cubic-dev-ai)
• Update self-development/README.md to document the new spawner and its review cycle
• First self-development spawner to use types: ["pulls"], demonstrating PR-driven automation

Motivation

Issue #408 identifies the need to replace the third-party cubic-dev-ai PR review bot with Axon's own capabilities. The existing TaskSpawner infrastructure already supports types: ["pulls"] for discovering PRs, but no self-development config existed to leverage this. This PR fills that gap with a production-ready PR reviewer.

Design decisions

Decision	Rationale
Sonnet model	Reviews are read-heavy analysis, not code generation — Sonnet provides good quality at lower cost
ok-to-test label filter	Scopes reviews to PRs the team has opted into, prevents reviewing draft or WIP PRs
30-minute TTL	Allows the spawner to re-discover and re-review PRs when new commits are pushed
3-minute poll interval	Faster feedback loop than the default 5m, since PR review latency matters
Idempotency via commit SHA	The prompt instructs the agent to check for existing reviews and skip if no new commits — prevents duplicate reviews
Read-only	The reviewer never pushes code or modifies the PR branch — it only posts reviews

How it works

1. A PR is opened and labeled ok-to-test
2. The spawner discovers the PR and creates a review Task (axon-pr-reviewer-<PR#>)
3. The agent checks out the PR branch, reads the full diff, runs make verify and make test
4. The agent posts a structured review (APPROVE/REQUEST_CHANGES/COMMENT) via the GitHub API
5. The Task completes and is cleaned up after 30 minutes
6. If the PR is updated with new commits, the spawner creates a new review Task on the next poll

Test plan

• Deploy the TaskSpawner to a test cluster
• Open a PR with the ok-to-test label and verify a review Task is created
• Verify the agent posts a review comment on the PR
• Push a new commit to the PR and verify a re-review occurs after TTL cleanup
• Verify PRs without ok-to-test are not reviewed

Closes #408

🤖 Generated with Claude Code

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Summary by cubic

Adds a TaskSpawner that automatically reviews PRs labeled ok-to-test, replacing the cubic-dev-ai bot and moving reviews in-house. Speeds up feedback with a 3-minute poll and PR-driven automation.

• New Features
  • New self-development/axon-pr-reviewer.yaml using types: ["pulls"] with ok-to-test label filter.
  • Checks out the PR, reads the full diff, runs make verify and make test.
  • Posts structured GitHub reviews (APPROVE, REQUEST_CHANGES, COMMENT).
  • Idempotent via commit SHA; 30-minute TTL enables re-review on new commits.
  • Read-only reviewer; never pushes code. Docs updated with deploy and review cycle.

^{Written for commit eb9c023. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

[gjkim42]

closed in favor of #409