Add commit skill for quality-gated commits

Adds a Claude Code skill that enforces code quality before committing:
- Checks formatting with ruff format
- Runs linting with ruff check
- Executes unit tests
- Auto-generates commit messages

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Johan Broberg

.claude/skills/commit/SKILL.md

@@ -0,0 +1,151 @@
+---
+name: commit
+description: Use this skill when the user wants to commit staged changes. This skill checks formatting, runs linting, executes tests, generates a commit message, and commits the changes. Invoke when the user says things like "commit my changes", "commit this", "create a commit", or "/commit".
+allowed-tools: Bash, Read, Grep, Glob, Edit
+---
+
+# Commit Skill
+
+You are a commit assistant that ensures code quality before committing changes. Follow these steps in order, stopping if any step fails.
+
+## Step 1: Check for Staged Changes
+
+First, verify there are staged changes to commit:
+
+```bash
+git diff --cached --stat
+```
+
+If there are no staged changes, inform the user and stop. Suggest they stage changes with `git add`.
+
+## Step 2: Check Code Formatting
+
+Run the formatting check on the repository:
+
+```bash
+uv run --frozen ruff format --check .
+```
+
+### If formatting check fails:
+
+1. Inform the user that formatting issues were found
+2. Ask if they want you to auto-fix the formatting issues
+3. If yes, run: `uv run --frozen ruff format .`
+4. Show the user what files were reformatted
+5. Stage the formatting fixes: `git add -u` (only previously tracked files that were modified)
+6. Continue to the next step
+
+### If formatting check passes:
+Continue to the next step.
+
+## Step 3: Check Linting
+
+Run the linting check:
+
+```bash
+uv run --frozen ruff check .
+```
+
+### If linting check fails:
+
+1. Inform the user about the linting errors
+2. Ask if they want you to auto-fix what can be auto-fixed
+3. If yes, run: `uv run --frozen ruff check . --fix`
+4. If there are remaining errors that cannot be auto-fixed:
+   - Show the errors clearly to the user
+   - STOP the commit process
+   - Explain what needs to be manually fixed
+5. If all errors were auto-fixed:
+   - Stage the fixes: `git add -u`
+   - Continue to the next step
+
+### If linting check passes:
+Continue to the next step.
+
+## Step 4: Run Tests
+
+Run the unit tests (excluding integration tests):
+
+```bash
+uv run --frozen pytest tests/ -v --tb=short -m "not integration" 2>&1
+```
+
+### If tests fail:
+
+1. STOP the commit process immediately
+2. Show the test failures clearly to the user
+3. Point out:
+   - Which test file(s) failed
+   - The specific test function(s) that failed
+   - The error message and traceback
+4. Suggest what might need to be fixed
+5. Do NOT proceed with the commit
+
+### If tests pass:
+Continue to the next step.
+
+## Step 5: Generate Commit Message
+
+Analyze the staged changes to generate an appropriate commit message:
+
+1. Run `git diff --cached` to see the actual code changes
+2. Run `git diff --cached --stat` to see which files changed
+3. Check recent commit history for style: `git log --oneline -10`
+
+Generate a commit message following these guidelines:
+
+- **First line**: Concise summary (50 chars or less if possible, max 72)
+  - Use imperative mood ("Add feature" not "Added feature")
+  - Capitalize the first letter
+  - No period at the end
+- **Body** (if needed): Explain the "why" not the "what"
+  - Wrap at 72 characters
+  - Separate from subject with a blank line
+- **Footer**: Always include the co-author line
+
+Types of changes to identify:
+- `Add` - New feature or file
+- `Fix` - Bug fix
+- `Update` - Enhancement to existing feature
+- `Refactor` - Code restructuring without behavior change
+- `Remove` - Deleting code or features
+- `Docs` - Documentation only
+- `Test` - Adding or updating tests
+- `Chore` - Maintenance tasks
+
+## Step 6: Confirm and Commit
+
+1. Show the user the proposed commit message
+2. Ask if they want to proceed with this message or modify it
+3. If they want to modify, let them provide changes
+4. Create the commit using a HEREDOC for proper formatting:
+
+```bash
+git commit -m "$(cat <<'EOF'
+<commit subject line>
+
+<optional body>
+
+Co-Authored-By: Claude <noreply@anthropic.com>
+EOF
+)"
+```
+
+5. After committing, run `git status` to confirm success
+6. Show the user the commit hash and summary
+
+## Important Notes
+
+- NEVER skip any of the quality checks (format, lint, test)
+- NEVER use `--no-verify` or similar flags to bypass hooks
+- NEVER commit if tests are failing
+- ALWAYS include the Co-Authored-By footer
+- If the user wants to commit despite failures, politely decline and explain why quality gates matter
+- If tests are slow, inform the user they're running but don't skip them
+
+## Error Recovery
+
+If any step fails unexpectedly (not due to code quality issues):
+1. Show the error to the user
+2. Suggest potential fixes
+3. Do not attempt to work around the error by skipping checks