chore: add ruff formatter, .gitignore, and uv convention (#40)

* chore: add ruff formatter, .gitignore, and uv convention

- Add ruff as dev dependency with basic config
- Add PostToolUse hook to auto-run ruff on .py edits
- Create .gitignore to exclude __pycache__ and settings.local.json
- Document uv run convention in CLAUDE.md
- Add CLAUDE.md, .claude/settings.json, and skills
- Apply ruff formatting to existing Python files

* fix: address CR feedback on hooks and uv run convention

- Fix hooks to read file_path from stdin JSON via jq instead of
  nonexistent $CLAUDE_FILE env var
- Update CLAUDE.md commands to use uv run python3 consistently
- Update skills to use uv run for python/dedup commands

tests/test_create_listing.py

@@ -133,7 +133,7 @@ class TestGenerateReadme:
         f = make_png(tmp_path, "smile.png")
         create_listing.generate_readme([f])
         content = (tmp_path / "README.md").read_text()
-        assert ':smile:' in content
+        assert ":smile:" in content
 
 
 class TestGenerateHtml: