chore: Add PR guidelines to cursor rules (#194)

## Summary

Adds cursor rules for PR best practices and guidelines for updating PR
titles/descriptions. Also enables Gemini reviews on draft PRs.

## Changes

- Added `.cursor/rules/pull-requests-best-practices.mdc` with guidelines
for:
  - PR title requirements (conventional commit format)
- PR description requirements (must include summary, issue references,
changes, impact)
  - Background agent PR requirements
  - PR template structure
- Added `.cursor/rules/updating-pr-descriptions.mdc` with instructions
for:
  - Using GitHub API to update PR titles/descriptions reliably
  - Workflow examples for updating PRs
- Updated `.gemini/config.yaml` to set `include_drafts: true` so Gemini
reviews draft PRs

## Impact / Benefits

- Ensures all PRs (including those from background agents) have proper
titles and descriptions
- Provides clear guidelines for referencing issues in PRs
- Enables code reviews on draft PRs via Gemini
- Documents the reliable method for updating PR titles/descriptions
using GitHub API

## Files Modified

- `.cursor/rules/pull-requests-best-practices.mdc` (new)
- `.cursor/rules/updating-pr-descriptions.mdc` (new)
- `.gemini/config.yaml` (modified)

Author: andeplane

.cursor/rules/pull-requests-best-practices.mdc

@@ -0,0 +1,56 @@
+---
+alwaysApply: false
+---
+
+# Pull Request Best Practices
+
+## PR Titles and Descriptions
+
+### Title Requirements
+- All PR titles MUST follow conventional commit format with prefixes:
+  - `fix:` for bug fixes
+  - `feat:` for new features
+  - `refactor:` for code refactoring
+  - `chore:` for maintenance tasks
+  - `docs:` for documentation changes
+  - `test:` for test-related changes
+  - `style:` for formatting changes
+- Titles should be descriptive and clearly indicate what the PR does
+- NEVER use generic titles like "Solve issue X and create PR" or "Fix issue Y"
+- Include the key change in the title (e.g., "fix: ColorModifier bugs - swapped min/max calculation")
+
+### Description Requirements
+- All PR descriptions MUST include:
+  1. A clear summary section explaining what the PR does
+  2. Reference to related GitHub issues using "Fixes #XXX" or "Closes #XXX" format
+  3. A "Changes" section listing what was modified
+  4. An "Impact" or "Benefits" section explaining why this change matters
+  5. Reference to any prerequisites or related PRs if applicable
+
+### Background Agent PRs
+- When creating PRs via background agents or automated tools:
+  - Always reference the related GitHub issue number in the title or description
+  - Use descriptive titles that explain the actual change, not just "Solve issue X"
+  - Include proper description sections as outlined above
+  - Ensure the PR title matches the issue's title or key change
+
+### PR Template Structure
+
+All PRs should follow this structure:
+```
+## Summary
+[Clear one-paragraph explanation of what this PR does]
+
+Fixes #XXX (or Closes #XXX)
+
+## Changes
+- [List of specific changes made]
+
+## Impact / Benefits
+[Explain why this change matters]
+
+## Files Modified
+- [List of files changed, if not obvious from changes]
+
+[Any additional context, testing notes, etc.]
+```

.cursor/rules/updating-pr-descriptions.mdc

@@ -0,0 +1,51 @@
+---
+alwaysApply: false
+---
+
+# Updating PR Descriptions and Titles
+
+## When Updating Existing PRs
+
+When updating PR titles or descriptions:
+1. Use GitHub API directly via `gh api` command for reliable updates
+2. The `gh pr edit` command may fail silently, so prefer the API approach
+3. For large bodies, use a temporary markdown file and read with `$(cat file.md)`
+
+## Method
+
+Use this format for reliable PR updates:
+
+```bash
+REPO=$(gh repo view --json owner,name -q '.owner.login + "/" + .name')
+gh api repos/$REPO/pulls/XXX -X PATCH \
+  -f title="fix: Descriptive title" \
+  -f body="$(cat pr_body.md)"
+```
+
+### Example Workflow
+
+1. Create a temporary markdown file with the PR body:
+   ```bash
+   cat > pr_body.md << 'EOF'
+   ## Summary
+   [Description here]
+   Fixes #XXX
+   EOF
+   ```
+
+2. Update the PR using GitHub API:
+   ```bash
+   REPO=$(gh repo view --json owner,name -q '.owner.login + "/" + .name')
+   gh api repos/$REPO/pulls/XXX -X PATCH \
+     -f title="fix: Descriptive title" \
+     -f body="$(cat pr_body.md)"
+   ```
+
+3. Clean up the temporary file:
+   ```bash
+   rm pr_body.md
+   ```
+
+## Notes
+- Always verify the update worked by checking the PR with `gh pr view XXX`
+- The GitHub API method is more reliable than `gh pr edit` which can fail silently

.gemini/config.yaml

@@ -8,6 +8,6 @@ code_review:
     help: false
     summary: true
     code_review: true
-    include_drafts: false
+    include_drafts: true
 
 ignore_patterns: []