Code review checklist documented

Without a PR template or documented code review checklist, review quality is entirely reviewer-dependent — type safety checks, test coverage verification, and breaking change documentation happen only when a reviewer happens to think of them. ISO 25010:2011 §6.5.3 classifies undocumented review processes as a maintainability defect. PR templates enforce a minimum bar on every PR: the author must explicitly confirm that tests pass, lint is clean, and breaking changes are documented — reducing the rate of issues that slip through to main.

Add a pull request template at .github/PULL_REQUEST_TEMPLATE.md. It pre-populates every new PR description with the checklist, so authors must actively uncheck items rather than passively forgetting them.

<!-- .github/PULL_REQUEST_TEMPLATE.md -->
## Summary
Brief description of the change and why it was made.

## Type of Change
- [ ] Bug fix
- [ ] New feature
- [ ] Refactor
- [ ] Documentation

## Checklist
- [ ] No new TypeScript errors (`npm run build` passes)
- [ ] Tests added or updated for changed logic
- [ ] `npm run lint` passes with no warnings
- [ ] No `console.log` or `@ts-ignore` added without comment
- [ ] Breaking changes documented in PR description

• ID: code-review-checklist

• Severity: info

• What to look for: Check for .github/PULL_REQUEST_TEMPLATE.md or .github/pull_request_template.md — this file pre-populates the PR description with a checklist when a new pull request is created. Also check for docs/CODE_REVIEW.md, CONTRIBUTING.md (which may include a review section), or any documented review standards. A PR template typically includes: type safety checklist, test coverage confirmation, documentation update check, and deployment considerations. Without a template, code review quality depends entirely on the reviewer's discipline.

• Pass criteria: Enumerate all relevant code locations. A pull request template or documented code review checklist exists.

• Fail criteria: No PR template and no documented review standards.

• Skip (N/A) when: Solo project where pull requests are not used (single developer, direct commits to main). Still good practice, but genuinely not applicable.

• Detail on fail: "No pull request template or code review checklist found in .github/ or docs/"

• Remediation: Add a pull request template:

  <!-- .github/PULL_REQUEST_TEMPLATE.md -->
  ## Summary
  Brief description of the change and why it was made.
  
  ## Type of Change
  - [ ] Bug fix
  - [ ] New feature
  - [ ] Refactor
  - [ ] Documentation
  
  ## Checklist
  - [ ] No new TypeScript errors (`npm run build` passes)
  - [ ] Tests added or updated for changed logic
  - [ ] `npm run lint` passes with no warnings
  - [ ] No `console.log` or `@ts-ignore` added without comment
  - [ ] Breaking changes documented in PR description