arch: split ConfigRepository, extract polling, consolidate conversions, decouple protocol

- Value↔JSON: From impls on domain Value behind `json` feature, delete 4 duplicate converters
- ConfigRepository split into ConfigRepository (12), UserRepository (3), WidgetStateCache (2)
- polling orchestration moved from bootstrap to application::polling_service
- WidgetRenderer in client-domain owns scroll/cache, both clients use it
- network loop consolidated into client-application::run_connection_loop
- protocol crate drops domain dep, Wire↔Domain conversions move to adapters

crates/client-application/tests/conversion_tests.rs

@@ -0,0 +1,151 @@
+use client_application::conversions::{
+    wire_to_display_hint, wire_to_layout, wire_to_value, wire_to_widget_state,
+};
+use domain::{
+    AlignItems, ContainerNode, Direction, DisplayHint, DisplayHintKind, JustifyContent,
+    LayoutChild, LayoutNode, Sizing, Value, WidgetError, WidgetState,
+};
+use protocol::{
+    WireContainerNode, WireDirection, WireDisplayHint, WireKeyValue, WireLayoutChild,
+    WireLayoutNode, WireSizing, WireValue, WireWidgetError, WireWidgetState,
+};
+use std::collections::BTreeMap;
+
+fn value_to_wire(v: &Value) -> WireValue {
+    match v {
+        Value::Null => WireValue::Null,
+        Value::Bool(b) => WireValue::Bool(*b),
+        Value::Number(n) => WireValue::Number(*n),
+        Value::String(s) => WireValue::String(s.clone()),
+        Value::Array(arr) => WireValue::Array(arr.iter().map(value_to_wire).collect()),
+        Value::Object(map) => WireValue::Object(
+            map.iter()
+                .map(|(k, v)| (k.clone(), value_to_wire(v)))
+                .collect(),
+        ),
+    }
+}
+
+#[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 = value_to_wire(&original);
+    let roundtripped = wire_to_value(wire);
+    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 {
+        data: original
+            .data
+            .iter()
+            .map(|(k, v)| WireKeyValue {
+                key: k.clone(),
+                value: value_to_wire(v),
+            })
+            .collect(),
+        error: Some(WireWidgetError::SourceUnavailable),
+    };
+    let roundtripped = wire_to_widget_state(wire);
+    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,
+        justify_content: JustifyContent::Start,
+        align_items: AlignItems::Stretch,
+        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,
+                    justify_content: JustifyContent::Start,
+                    align_items: AlignItems::Stretch,
+                    children: vec![LayoutChild {
+                        sizing: Sizing::Flex(1),
+                        node: LayoutNode::Leaf(2),
+                    }],
+                }),
+            },
+        ],
+    });
+
+    let wire = WireLayoutNode::Container(WireContainerNode {
+        direction: WireDirection::Row,
+        gap: 4,
+        padding: 2,
+        justify_content: protocol::WireJustifyContent::Start,
+        align_items: protocol::WireAlignItems::Stretch,
+        children: vec![
+            WireLayoutChild {
+                sizing: WireSizing::Flex(1),
+                node: WireLayoutNode::Leaf(1),
+            },
+            WireLayoutChild {
+                sizing: WireSizing::Fixed(100),
+                node: WireLayoutNode::Container(WireContainerNode {
+                    direction: WireDirection::Column,
+                    gap: 2,
+                    padding: 0,
+                    justify_content: protocol::WireJustifyContent::Start,
+                    align_items: protocol::WireAlignItems::Stretch,
+                    children: vec![WireLayoutChild {
+                        sizing: WireSizing::Flex(1),
+                        node: WireLayoutNode::Leaf(2),
+                    }],
+                }),
+            },
+        ],
+    });
+
+    let roundtripped = wire_to_layout(wire);
+    assert_eq!(original, roundtripped);
+}
+
+#[test]
+fn display_hint_converts_to_wire_and_back() {
+    for (hint, wire_kind) in [
+        (
+            DisplayHintKind::IconValue,
+            protocol::WireDisplayHintKind::IconValue,
+        ),
+        (
+            DisplayHintKind::TextBlock,
+            protocol::WireDisplayHintKind::TextBlock,
+        ),
+        (
+            DisplayHintKind::KeyValue,
+            protocol::WireDisplayHintKind::KeyValue,
+        ),
+    ] {
+        let original = DisplayHint::new(hint);
+        let wire = WireDisplayHint::new(wire_kind);
+        let roundtripped = wire_to_display_hint(wire);
+        assert_eq!(original, roundtripped);
+    }
+}