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/protocol/tests/conversion_tests.rs

@@ -1,86 +0,0 @@
-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;
-
-#[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,
-        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 = (&original).into();
-    let roundtripped: LayoutNode = wire.into();
-    assert_eq!(original, roundtripped);
-}
-
-#[test]
-fn display_hint_converts_to_wire_and_back() {
-    for hint in [
-        DisplayHint::new(DisplayHintKind::IconValue),
-        DisplayHint::new(DisplayHintKind::TextBlock),
-        DisplayHint::new(DisplayHintKind::KeyValue),
-    ] {
-        let wire: WireDisplayHint = (&hint).into();
-        let roundtripped: DisplayHint = wire.into();
-        assert_eq!(hint, roundtripped);
-    }
-}