feat(windows): persistance et restauration des fenêtres au redémarrage (#40)

Persiste l'état des fenêtres (layout/position) et le restaure au
relancement de l'application. Découpage hexagonal :
- domaine : modèle et port d'état des fenêtres (layout, ports)
- application : use cases de persistance/restauration
- infrastructure : store window_state (adapter de persistance)
- présentation : câblage app-tauri (state, commands, lib)
Couvert par des tests ciblés domaine/application/infrastructure.

Depend de #39 (fermeture des fenêtres auxiliaires).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/domain/tests/window.rs

@@ -3,8 +3,9 @@
 //! window is dropped; an active moved tab hands activity back to a sibling.
 
 use domain::{
-    LayoutError, LayoutNode, LayoutTree, LeafCell, NodeId, ProjectId, Tab, TabId, Window, WindowId,
-    Workspace,
+    LayoutError, LayoutNode, LayoutTree, LeafCell, NodeId, PersistedMonitorState,
+    PersistedWindowKind, PersistedWindowPosition, PersistedWindowSize, PersistedWindowState,
+    ProjectId, Tab, TabId, Window, WindowId, WindowStateSnapshot, Workspace,
 };
 use uuid::Uuid;
 
@@ -94,3 +95,43 @@ fn move_non_active_tab_leaves_source_active_unchanged() {
     assert_eq!(source.active_tab, tid(1), "active tab unchanged");
     assert_eq!(source.tabs.len(), 1);
 }
+
+#[test]
+fn window_state_snapshot_round_trips_with_camel_case_schema() {
+    let snapshot = WindowStateSnapshot::new(vec![PersistedWindowState {
+        label: "view-tickets-0000000000000000000000000000002a".to_owned(),
+        kind: PersistedWindowKind::View,
+        panel: Some("tickets".to_owned()),
+        project_id: Some(ProjectId::from_uuid(Uuid::from_u128(42))),
+        url: Some(
+            "index.html?panel=tickets&project=00000000-0000-0000-0000-00000000002a".to_owned(),
+        ),
+        visible: true,
+        maximized: false,
+        fullscreen: false,
+        outer_position: Some(PersistedWindowPosition { x: 12, y: 34 }),
+        outer_size: Some(PersistedWindowSize {
+            width: 1200,
+            height: 800,
+        }),
+        monitor: Some(PersistedMonitorState {
+            name: Some("HDMI-1".to_owned()),
+            scale_factor: Some(1.25),
+            position: Some(PersistedWindowPosition { x: 0, y: 0 }),
+            size: Some(PersistedWindowSize {
+                width: 1920,
+                height: 1080,
+            }),
+        }),
+        last_focused_at: Some(123),
+    }]);
+
+    let json = serde_json::to_string(&snapshot).unwrap();
+    assert!(json.contains("\"projectId\""), "json was {json}");
+    assert!(json.contains("\"outerPosition\""), "json was {json}");
+    assert!(json.contains("\"scaleFactor\""), "json was {json}");
+    assert!(!json.contains("project_id"), "no snake_case leak: {json}");
+
+    let decoded: WindowStateSnapshot = serde_json::from_str(&json).unwrap();
+    assert_eq!(decoded, snapshot);
+}