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/protocol/tests/conversion_tests.rs

@@ -0,0 +1,82 @@
+use std::collections::BTreeMap;
+use domain::{
+    Value, WidgetState, WidgetError, DisplayHint,
+    LayoutNode, ContainerNode, LayoutChild, Direction, Sizing,
+};
+use protocol::{
+    WireValue, WireWidgetState, WireWidgetError, WireDisplayHint,
+    WireLayoutNode, WireContainerNode, WireLayoutChild, WireDirection, WireSizing,
+    WireKeyValue,
+};
+
+#[test]
+fn value_converts_to_wire_and_back() {
+    let original = Value::Object(BTreeMap::from([
+        ("items".into(), Value::Array(vec![
+            Value::String("hello".into()),
+            Value::Number(42.0),
+            Value::Bool(true),
+            Value::Null,
+        ])),
+    ]));
+
+    let wire: WireValue = (&original).into();
+    let roundtripped: Value = wire.into();
+    assert_eq!(original, roundtripped);
+}
+
+#[test]
+fn widget_state_with_error_converts_to_wire_and_back() {
+    let original = WidgetState {
+        data: BTreeMap::from([
+            ("temp".into(), Value::Number(5.4)),
+        ]),
+        error: Some(WidgetError::SourceUnavailable),
+    };
+
+    let wire: WireWidgetState = (&original).into();
+    let roundtripped: WidgetState = wire.into();
+    assert_eq!(original, roundtripped);
+}
+
+#[test]
+fn layout_tree_converts_to_wire_and_back() {
+    let original = LayoutNode::Container(ContainerNode {
+        direction: Direction::Row,
+        gap: 4,
+        padding: 2,
+        children: vec![
+            LayoutChild {
+                sizing: Sizing::Flex(1),
+                node: LayoutNode::Leaf(1),
+            },
+            LayoutChild {
+                sizing: Sizing::Fixed(100),
+                node: LayoutNode::Container(ContainerNode {
+                    direction: Direction::Column,
+                    gap: 2,
+                    padding: 0,
+                    children: vec![
+                        LayoutChild {
+                            sizing: Sizing::Flex(1),
+                            node: LayoutNode::Leaf(2),
+                        },
+                    ],
+                }),
+            },
+        ],
+    });
+
+    let wire: WireLayoutNode = (&original).into();
+    let roundtripped: LayoutNode = wire.into();
+    assert_eq!(original, roundtripped);
+}
+
+#[test]
+fn display_hint_converts_to_wire_and_back() {
+    for hint in [DisplayHint::IconValue, DisplayHint::TextBlock, DisplayHint::KeyValue] {
+        let wire: WireDisplayHint = (&hint).into();
+        let roundtripped: DisplayHint = wire.into();
+        assert_eq!(hint, roundtripped);
+    }
+}