chore: consolidate deps into pyproject.toml and add CLAUDE.md

Remove requirements.txt and move all dependencies (torch, huggingface_hub,
einops, einx, spaces) into pyproject.toml for uv-managed workflow.
Update README install instructions to use `uv sync`.
Add CLAUDE.md with architecture notes for Claude Code.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,54 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+```bash
+# Install dependencies
+uv sync
+
+# Run the app
+uv run python app.py
+```
+
+App serves at **http://127.0.0.1:7860**
+
+Set `HF_TOKEN` environment variable to authenticate with Hugging Face (required for Godzilla model download).
+
+## Architecture
+
+**SYNTHIA** is a browser-based MIDI keyboard with AI continuation. Three layers:
+
+- **Backend** (`app.py`, `engines.py`, `midi_model.py`, `midi.py`, `config.py`): Python/Gradio
+- **Frontend** (`static/keyboard.js`, `static/styles.css`, `keyboard.html`): Tone.js audio synthesis
+- **Bridge**: Hidden Gradio components (textboxes + buttons with `elem_id`s) act as the API layer between JS and Python
+
+### Frontend → Backend Communication Pattern
+
+JavaScript communicates with Python by:
+1. Writing a JSON string into a hidden `gr.Textbox` (`elem_id="vk_engine_input"`, etc.)
+2. Programmatically clicking a hidden `gr.Button` (`elem_id="vk_engine_cpu_btn"` or `"vk_engine_gpu_btn"`)
+3. Reading the JSON response from a hidden output `gr.Textbox`
+
+This pattern is used for all three bridges: `get_config`, `save_midi`, and `process_engine` (CPU and GPU variants).
+
+### Engine System
+
+Engines live in `engines.py` and are registered in `EngineRegistry._engines`. Each engine class has a `process(events, options, request, device)` method that takes/returns MIDI event dicts with keys: `type`, `note`, `velocity`, `time`, `channel`.
+
+Current engines: `parrot`, `reverse_parrot`, `godzilla_continue`.
+
+To add a new engine: create a class in `engines.py`, register it in `EngineRegistry._engines`, and add a tooltip in `keyboard.js` (`populateEngineSelect()`).
+
+### GPU vs CPU
+
+`process_engine_event_bridge_gpu` is decorated with `@spaces.GPU(duration=120)` for Hugging Face Spaces. The `device` parameter (`"cuda"` or `"cpu"`) is forwarded all the way to the model inference.
+
+### Godzilla Model
+
+`midi_model.py` handles the Hugging Face transformer model. It's preloaded in a background daemon thread at startup (`start_background_preload()`). `get_model("godzilla")` returns a cached singleton. The model tokenizes MIDI events, runs autoregressive generation, then detokenizes back to events.
+
+### Config as Single Source of Truth
+
+`config.py` defines `INSTRUMENTS`, `KEYBOARD_KEYS`, and `KEYBOARD_SHORTCUTS`. These are served to the frontend via the `get_config` bridge endpoint — the frontend does not hardcode them.

README.md

@@ -18,7 +18,7 @@ Play, record, and let AI continue your musical phrases in real-time. 🎹
 
 ```bash
 # Install dependencies
-uv pip install -r requirements.txt
+uv sync
 
 # Run the app
 uv run python app.py

pyproject.toml

@@ -5,6 +5,11 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.10"
 dependencies = [
+    "einops>=0.6",
+    "einx>=0.3.0",
     "gradio==5.49.1",
+    "huggingface-hub>=1.4.1",
     "mido>=1.3.3",
+    "spaces>=0.47.0",
+    "torch>=2.10.0",
 ]

requirements.txt

@@ -1,7 +0,0 @@
-gradio
-mido
-torch
-huggingface_hub
-einops>=0.6
-einx
-spaces