Align docs with ESP32-S3 dashboard architecture

docs/decisions.md

@@ -20,38 +20,45 @@ Reason:
 
 The ESP32 is installed near the electrical system and should continue operating even if the dashboard is disconnected.
 
-## Decision: Pico Is a Dashboard, Not the Controller
+## Decision: Waveshare ESP32-S3 Is the Dashboard Client
 
-The Pico dashboard is responsible for user interaction.
+The Waveshare ESP32-S3 touchscreen dashboard is responsible for local user interaction.
 
-It should not own critical control state.
+It connects to the Cargo ESP32 access point and consumes the HTTP API. It should not own critical control state.
 
 Reason:
 
 The dashboard may reboot, disconnect, or be removed without disabling the controller.
 
-## Decision: UART Is the Primary Dashboard Link
+## Decision: HTTP Is the Primary Dashboard Link
 
-UART is the preferred Pico-to-ESP32 communication path.
+HTTP over the Cargo ESP32 local WiFi network is the preferred dashboard-to-controller communication path.
 
 Reason:
 
-- Simple wiring
-- Deterministic
-- No WiFi dependency
-- Works offline
-- Easier to debug electrically
+- Matches the WebUI and future integration contract
+- Avoids a dedicated dashboard data cable
+- Supports the Waveshare ESP32-S3 dashboard target
+- Keeps the dashboard a simple client
 
-HTTP remains useful for setup, debugging, and future web UI.
+The Cargo ESP32 AP remains available for local operation without internet.
+
+## Decision: UART Is Optional Diagnostics
+
+UART JSON may remain useful for service diagnostics, simulator work, or alternate clients.
+
+Reason:
+
+USB serial and UART are useful recovery/debug paths, but the dashboard architecture should not depend on a Pico or UART cable.
 
 ## Decision: HTTP and UART Should Share a Data Model
 
 The same status/config model should be used across:
 
-- UART
 - HTTP
 - Simulator
 - Future MQTT/Home Assistant integrations
+- Optional UART diagnostics
 
 Reason:
 
@@ -177,3 +184,13 @@ Cloud dashboards and remote access are not current priorities.
 Reason:
 
 The core controller/dashboard system should be reliable locally before remote features are considered.
+
+## Decision: Future Pi Zero Is Optional
+
+A Pi Zero may be added later for long-term logging, charts, dashboards, or local integrations.
+
+It must not own relay control, BMS state, alarm authority, or persistent controller configuration.
+
+Reason:
+
+The Cargo ESP32 must continue operating as the controller and source of truth without any higher-level computer powered on.