feat: add issue number detection to pr command

The /pr command now automatically detects issue numbers from:
1. Explicit arguments (e.g., /pr 123 or /pr 123,456)
2. Branch name patterns (e.g., fix/123-bug, issue-456-feature)

Adds "Closes #X" lines to PR body to auto-close issues on merge.

.claude/commands/pr.md

@@ -4,10 +4,21 @@ description: Create a PR to main branch using conventional commit style for the
 
 Create a pull request from the current branch to the `main` branch.
 
+## Arguments
+
+The user may provide issue numbers that this PR fixes: `$ARGUMENTS`
+
+- If provided (e.g., `123` or `123,456`), use these issue numbers
+- If not provided, check the branch name for issue numbers (e.g., `fix/123-bug` or `issue-456-feature` → extract `123` or `456`)
+- If no issues are found, omit the "Closes" section
+
+## Steps
+
 First, analyze the current branch to understand what changes have been made:
 1. Run `git log --oneline -10` to see recent commit history and understand commit style
 2. Run `git log main..HEAD --oneline` to see all commits on this branch that will be included in the PR
 3. Run `git diff main...HEAD --stat` to see a summary of file changes
+4. Run `git branch --show-current` to get the branch name for issue detection (if no explicit issues provided)
 
 Then generate a PR title that:
 - Follows conventional commit format (e.g., `fix:`, `feat:`, `chore:`, `refactor:`)
@@ -16,17 +27,24 @@ Then generate a PR title that:
 
 Generate a PR body with:
 - A `## Summary` section with 1-3 bullet points describing the changes
+- A `Closes #X` line for each issue number (if any were provided or detected from branch name)
 
 Finally, create the PR using the gh CLI:
 ```
 gh pr create --base main --title "<generated title>" --body "$(cat <<'EOF'
 ## Summary
 <bullet points>
+
+Closes #<issue1>
+Closes #<issue2>
 EOF
 )"
 ```
 
+Note: Omit the "Closes" lines entirely if no issues are associated with this PR.
+
 IMPORTANT:
 - Do NOT include any Claude Code attribution in the PR
 - Keep the summary concise (1-3 bullet points maximum)
 - Use the conventional commit prefix that best matches the changes (fix, feat, chore, refactor, docs, etc.)
+- The `Closes #X` syntax will automatically close the referenced issues when the PR is merged