add all crates: domain, protocol, application, client, adapters, ESP32 firmware

Server: domain (entities, value objects, ports), protocol (postcard wire types),
application (config service, data projection), adapters (config-memory, tcp-server),
bootstrap (composition root with fake data).

Client: client-domain (layout engine, render tree, HAL ports),
client-application (message handling, repaint commands),
adapters (tcp-client, display-terminal), client-desktop (end-to-end working).

ESP32: client-esp32 firmware with ILI9341 display over SPI, WiFi networking.
Display test verified on hardware — landscape orientation, text rendering works.

60 workspace tests, all passing.

crates/domain/src/entities/widget_config.rs

@@ -0,0 +1,70 @@
+use std::collections::BTreeMap;
+use crate::value_objects::{DisplayHint, KeyMapping, Value, WidgetState};
+
+pub type WidgetId = u16;
+pub type DataSourceId = u16;
+
+const DEFAULT_MAX_DATA_SIZE: u16 = 2048;
+
+#[derive(Debug, Clone)]
+pub struct WidgetConfig {
+    pub id: WidgetId,
+    pub name: String,
+    pub display_hint: DisplayHint,
+    pub data_source_id: DataSourceId,
+    pub mappings: Vec<KeyMapping>,
+    pub max_data_size: u16,
+}
+
+impl WidgetConfig {
+    pub fn new(
+        id: WidgetId,
+        name: String,
+        display_hint: DisplayHint,
+        data_source_id: DataSourceId,
+        mappings: Vec<KeyMapping>,
+    ) -> Self {
+        Self {
+            id,
+            name,
+            display_hint,
+            data_source_id,
+            mappings,
+            max_data_size: DEFAULT_MAX_DATA_SIZE,
+        }
+    }
+
+    pub fn extract(&self, raw: &Value) -> WidgetState {
+        let budget = self.max_data_size as usize;
+        let mut used = 0usize;
+        let mut data = BTreeMap::new();
+
+        for mapping in &self.mappings {
+            if let Some((key, value)) = mapping.extract(raw) {
+                let key_cost = key.len();
+                let remaining = budget.saturating_sub(used + key_cost);
+                let value = Self::truncate_value(value, remaining);
+                used += key_cost + value.estimated_size();
+                data.insert(key, value);
+                if used >= budget {
+                    break;
+                }
+            }
+        }
+
+        WidgetState { data, error: None }
+    }
+
+    fn truncate_value(value: Value, max_bytes: usize) -> Value {
+        match value {
+            Value::String(s) if s.len() > max_bytes => {
+                let truncated: String = s.char_indices()
+                    .take_while(|(i, _)| *i < max_bytes)
+                    .map(|(_, c)| c)
+                    .collect();
+                Value::String(truncated)
+            }
+            other => other,
+        }
+    }
+}