feat(memory): config embedders (LOT C2) + suggestion contextuelle (LOT C3) + contexte projet partagé

- LOT C2 (§14.5.3) : use cases de configuration des embedders déclaratifs
  (List/Save/Delete + DescribeEmbedderEngines : modèles ONNX recommandés,
  environnement local détecté, stratégies compilées). UI EmbedderSettings.
- LOT C3 (§14.5.5) : suggestion contextuelle best-effort à l'activation quand la
  mémoire dépasse le budget de recall sans embedder configuré (event
  EmbedderSuggested, anti-spam 1×/session, « ne plus demander »).
- Contexte projet partagé .ideai/CONTEXT.md (model-agnostic) injecté à tous les
  agents/profils au lancement, avant la persona. UI ProjectContextPanel.

Tests : backend workspace vert (0 échec) ; frontend 306/306.

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

crates/app-tauri/tests/dto.rs

@@ -7,16 +7,16 @@ use app_tauri_lib::dto::{
     LayoutOperationDto, OpenTerminalRequestDto, ReattachResultDto, ResizeTerminalRequestDto,
     TerminalClosedDto, WriteTerminalRequestDto,
 };
+use app_tauri_lib::events::{DomainEventDto, DOMAIN_EVENT};
 use application::{CloseTerminalOutput, LayoutOperation, LoadLayoutOutput, OpenTerminalInput};
 use domain::{Direction, LayoutNode, LayoutTree, LeafCell, NodeId};
-use app_tauri_lib::events::{DomainEventDto, DOMAIN_EVENT};
 
 use application::{AppError, HealthInput};
 use domain::events::DomainEvent;
 use domain::ids::{AgentId, SessionId};
 use domain::ProjectId;
-use domain::TemplateVersion;
 use domain::TemplateId;
+use domain::TemplateVersion;
 use serde_json::json;
 use uuid::Uuid;
 
@@ -188,7 +188,10 @@ fn terminal_closed_dto_serialises_code_camel_case() {
 
     // Signalled (None) round-trips as null.
     let none = TerminalClosedDto::from(CloseTerminalOutput { code: None });
-    assert_eq!(serde_json::to_value(&none).unwrap(), json!({ "code": null }));
+    assert_eq!(
+        serde_json::to_value(&none).unwrap(),
+        json!({ "code": null })
+    );
 }
 
 #[test]
@@ -198,7 +201,10 @@ fn reattach_result_dto_serialises_camel_case() {
         scrollback: vec![104, 105],
     };
     let v = serde_json::to_value(&dto).unwrap();
-    assert_eq!(v, json!({ "sessionId": "sess-1", "scrollback": [104, 105] }));
+    assert_eq!(
+        v,
+        json!({ "sessionId": "sess-1", "scrollback": [104, 105] })
+    );
 }
 
 #[test]
@@ -327,7 +333,18 @@ fn layout_dto_round_trips_a_split_tree_shape() {
         conversation_id: None,
         agent_was_running: false,
     })
-    .split(nid(1), Direction::Column, LeafCell { id: nid(2), session: None, agent: None, conversation_id: None, agent_was_running: false }, nid(9))
+    .split(
+        nid(1),
+        Direction::Column,
+        LeafCell {
+            id: nid(2),
+            session: None,
+            agent: None,
+            conversation_id: None,
+            agent_was_running: false,
+        },
+        nid(9),
+    )
     .unwrap();
     let dto = LayoutDto::from(LoadLayoutOutput {
         layout_id: domain::LayoutId::new_random(),