Move all animations to Pico firmware, Pi becomes HTTP-serial bridge

Pico runs all 9 mood animations and jaw modes locally instead of
receiving per-LED serial commands from the Pi. New protocol: bare
integers for fire-and-forget jaw amplitude, "mood X" / "jaw X" for
mode switches. Cuts light_service.py from 409 to 193 lines.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -8,14 +8,15 @@ LED strip control for head-vixy (Vixy's robotic head) via Raspberry Pi Pico 2.
 ┌─────────────────┐     USB Serial      ┌──────────────────┐
 │  Raspberry Pi 5 │◄──────────────────►│  Pico 2          │
 │  (light_service)│    /dev/ttyACM0     │  (main.py)       │
-│  Port 8781      │                     │                  │
-└─────────────────┘                     │  GP0 → Jaw LEDs  │
-                                        │  GP1 → Mood LEDs │
+│  Port 8781      │                     │  Animation Engine │
+└─────────────────┘                     │                  │
+  HTTP-to-serial                        │  GP0 → Jaw LEDs  │
+  bridge                                │  GP1 → Mood LEDs │
                                         └──────────────────┘
 ```
 
-- **Raspberry Pi 5** - Runs Python service, HTTP API, animation logic
-- **Raspberry Pi Pico 2** - Controls LED strips via PIO, receives serial commands
+- **Raspberry Pi 5** - Thin HTTP-to-serial bridge, forwards mode commands
+- **Raspberry Pi Pico 2** - Runs all LED animations locally via PIO
 - **Mood strip**: 56x WS2812B LEDs on GP1
 - **Jaw strip**: 14x WS2812B LEDs on GP0 (index 0 damaged, use 1-13)
 
@@ -28,11 +29,12 @@ The BBB PRU approach burned 4 boards. Pico 2 is $5, runs MicroPython, has hardwa
 ```
 head-lights/
 ├── README.md              # This file
-├── light_service.py       # Pi service (animations + HTTP API)
+├── light_service.py       # Pi service (HTTP-to-serial bridge)
 ├── requirements.txt       # Python deps (pyserial)
 ├── vixy-lights.service    # systemd unit file
+├── docs/plans/            # Design documents
 └── firmware/
-    └── main.py            # Pico 2 MicroPython firmware
+    └── main.py            # Pico 2 MicroPython firmware (animation engine)
 ```
 
 ## States
@@ -49,7 +51,6 @@ head-lights/
 | love | Soft pink 💕 | Gentle breathing | Tender/affectionate |
 | sleep | Dim blue-gray | Very slow, dim | Low power/resting |
 
-
 ## API Endpoints
 
 ```
@@ -57,30 +58,26 @@ GET  /health      - Service health (includes serial connection status)
 GET  /state       - Current light state + jaw level
 POST /state       - Set state: {"state": "listening"}
 POST /jaw/level   - Set jaw level: {"level": 0-100}
+POST /jaw/mode    - Set jaw mode: {"mode": "talking"}
 ```
 
 **Port: 8781**
 
 ## Pico Serial Protocol
 
-Commands sent over USB serial at 115200 baud:
+All animations run on the Pico. The Pi sends mode commands over USB serial at 115200 baud:
 
-```
-<strip> <index> <r> <g> <b>   - Set single LED
-<strip> -1                     - Trigger strip update (show)
-<strip> clear                  - Clear strip
-<strip> fill <r> <g> <b>       - Fill entire strip (mood only)
-```
+| Command | Example | Response | Description |
+|---------|---------|----------|-------------|
+| `<integer>` | `72` | *(none)* | Jaw amplitude 0-100, fire-and-forget |
+| `mood <mode>` | `mood thinking` | `OK` | Switch mood animation |
+| `jaw <mode>` | `jaw talking` | `OK` | Switch jaw animation mode |
 
-Strip IDs: 0 = Jaw, 1 = Mood
+**Mood modes:** idle, listening, responding, pleasure, thinking, playful, commanding, love, sleep, off
 
-Examples:
-```
-1 0 255 0 0      # Set mood LED 0 to red
-1 -1             # Show mood strip
-0 clear          # Clear jaw strip
-1 fill 0 255 255 # Fill mood with cyan
-```
+**Jaw modes:** idle, talking, off
+
+Bare integers are the fast path for jaw amplitude during speech — minimal bytes, no response wait.
 
 ## Installation
 
@@ -122,7 +119,7 @@ curl http://head-vixy.local:8781/health
 # Get current state
 curl http://head-vixy.local:8781/state
 
-# Set state
+# Set mood state
 curl -X POST http://head-vixy.local:8781/state \
   -H "Content-Type: application/json" \
   -d '{"state": "thinking"}'
@@ -131,6 +128,11 @@ curl -X POST http://head-vixy.local:8781/state \
 curl -X POST http://head-vixy.local:8781/jaw/level \
   -H "Content-Type: application/json" \
   -d '{"level": 75}'
+
+# Set jaw mode
+curl -X POST http://head-vixy.local:8781/jaw/mode \
+  -H "Content-Type: application/json" \
+  -d '{"mode": "talking"}'
 ```
 
 ## Unified Head Control