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

CLAUDE.md

@@ -0,0 +1,52 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Personal emoji/emote collection for chat apps (Slack, Discord, etc.). Contains 3000+ custom emoji images in `emoji/` with Python tooling for maintenance: listing generation and perceptual deduplication.
+
+## Commands
+
+```bash
+# Install dependencies (uses uv package manager)
+uv sync
+
+# Regenerate README.md and index.html from emoji/ contents
+uv run python3 create_listing.py
+
+# Find duplicate emojis (dry run)
+uv run python3 dedup.py --dry-run
+
+# Find duplicates with custom threshold (0=exact match, default)
+uv run python3 dedup.py --threshold 5 --dry-run
+
+# Actually remove duplicates
+uv run python3 dedup.py --dir emoji/
+
+# Or via uv entry point
+uv run dedup --dry-run
+
+# Run tests
+uv run pytest
+
+# Run tests with verbose output
+uv run pytest -v
+```
+
+## Architecture
+
+Two standalone Python scripts, no shared modules:
+
+- **`create_listing.py`** — Generates `README.md` (HTML tables) and `index.html` (searchable dark-theme SPA) from all images in `emoji/`. No dependencies beyond stdlib. Both output files are auto-generated and committed by CI on push.
+
+- **`dedup.py`** — Finds and removes duplicate images using multi-algorithm perceptual hashing (pHash, aHash, dHash, colorHash). Uses Union-Find clustering. Animated GIFs get extra frame-by-frame verification including timing. Keeps alphabetically-first filename per duplicate group.
+
+## Key Conventions
+
+- Python >=3.11 required; dependencies managed via `uv` with `uv.lock`
+- Image formats: `.png`, `.gif`, `.jpg`, `.jpeg`
+- `README.md` and `index.html` are generated artifacts — edit the scripts, not the outputs
+- CI uses pinned action SHAs (not tags) for security
+- Dependency updates managed by Renovate bot
+- Always use `uv run` to execute Python commands (e.g. `uv run pytest`, `uv run ruff`, `uv run python3 script.py`) to ensure the correct virtualenv and dependencies are used