feat: scaffold tuimble TUI mumble client

Core modules: TUI app (textual), mumble protocol client,
audio pipeline (sounddevice + opus), push-to-talk with
kitty protocol / evdev / toggle backends. Config via TOML.

docs/CHEATSHEET.md

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+# Cheatsheet
+
+```
+make setup           setup venv + deps
+make run             launch tuimble
+make test            run tests
+make lint            check code style
+
+q                    quit
+space                push-to-talk (hold)
+Enter                send message
+```

docs/DEBUG.md

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+# Debugging
+
+## Verbose Mode
+
+```sh
+tuimble --verbose                # (planned)
+```
+
+## Common Issues
+
+### No audio devices found
+
+```sh
+python3 -c "import sounddevice; print(sounddevice.query_devices())"
+```
+
+Check that portaudio is installed and devices are accessible.
+
+### opuslib import error
+
+```sh
+python3 -c "import opuslib"
+```
+
+If this fails, install libopus: `apt install libopus0`
+
+### Kitty protocol not detected
+
+Verify terminal supports the Kitty keyboard protocol.
+Known working: Kitty, WezTerm, Ghostty, foot.
+
+### evdev permission denied
+
+```sh
+ls -la /dev/input/event*
+groups                           # should include 'input'
+```
+
+Add user to `input` group: `sudo usermod -aG input $USER`
+
+### Connection refused
+
+- Verify server address and port
+- Check firewall allows outbound TCP/UDP to port 64738
+- Test with: `nc -zv <host> 64738`

docs/INSTALL.md

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+# Installation
+
+## Prerequisites
+
+### System Libraries
+
+```sh
+# Debian/Ubuntu
+sudo apt install libopus0 libopus-dev portaudio19-dev
+
+# Fedora/RHEL
+sudo dnf install opus opus-devel portaudio-devel
+
+# Arch
+sudo pacman -S opus portaudio
+```
+
+### Python
+
+Python 3.11 or later required.
+
+## Setup
+
+```sh
+git clone <repo-url> ~/git/tuimble
+cd ~/git/tuimble
+make setup
+```
+
+## Verify
+
+```sh
+make test
+tuimble --version
+```
+
+## Optional: evdev PTT
+
+For Linux evdev push-to-talk (physical key detection):
+
+```sh
+pip install tuimble[evdev]
+sudo usermod -aG input $USER
+# Log out and back in for group change
+```
+
+## Symlink
+
+```sh
+ln -sf ~/git/tuimble/.venv/bin/tuimble ~/.local/bin/tuimble
+which tuimble
+```

docs/USAGE.md

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+# Usage
+
+## Running
+
+```sh
+tuimble                          # uses ~/.config/tuimble/config.toml
+tuimble --host mumble.example.com --user myname
+```
+
+## Key Bindings
+
+| Key | Action |
+|-----|--------|
+| `q` | Quit |
+| `space` | Push-to-talk (configurable) |
+| `Enter` | Send message |
+| `Ctrl+C` | Quit |
+
+## Push-to-Talk Modes
+
+- **hold** — hold key to transmit, release to stop (default)
+- **toggle** — press to start, press again to stop
+
+## Configuration
+
+See `~/.config/tuimble/config.toml`. All fields are optional;
+defaults connect to localhost:64738.