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/application/tests/agent_inspect.rs

@@ -192,7 +192,15 @@ fn profile(id: ProfileId) -> AgentProfile {
 }
 
 fn agent(id: AgentId, profile_id: ProfileId) -> Agent {
-    Agent::new(id, "Bob", "agents/bob.md", profile_id, AgentOrigin::Scratch, false).unwrap()
+    Agent::new(
+        id,
+        "Bob",
+        "agents/bob.md",
+        profile_id,
+        AgentOrigin::Scratch,
+        false,
+    )
+    .unwrap()
 }
 
 fn input(agent_id: AgentId) -> InspectConversationInput {
@@ -228,7 +236,10 @@ async fn supporting_inspector_propagates_details() {
     );
 
     let out = uc.execute(input(aid)).await.unwrap();
-    assert_eq!(out.details.last_topic.as_deref(), Some("refactor the parser"));
+    assert_eq!(
+        out.details.last_topic.as_deref(),
+        Some("refactor the parser")
+    );
     assert_eq!(out.details.token_count, Some(4242));
 
     // Routed the conversation id and the agent's isolated run dir (not the root).
@@ -270,8 +281,10 @@ async fn read_error_degrades_to_empty_details() {
     let aid = AgentId::from_uuid(Uuid::from_u128(42));
     let a = agent(aid, pid);
 
-    let (inspector, _seen) =
-        FakeInspector::new(true, InspectResult::Err(InspectError::Read("boom".to_owned())));
+    let (inspector, _seen) = FakeInspector::new(
+        true,
+        InspectResult::Err(InspectError::Read("boom".to_owned())),
+    );
 
     let uc = InspectConversation::new(
         Arc::new(FakeContexts::with_agent(&a)),
@@ -280,7 +293,13 @@ async fn read_error_degrades_to_empty_details() {
     );
 
     let out = uc.execute(input(aid)).await.unwrap();
-    assert_eq!(out.details, ConversationDetails { last_topic: None, token_count: None });
+    assert_eq!(
+        out.details,
+        ConversationDetails {
+            last_topic: None,
+            token_count: None
+        }
+    );
 }
 
 // ---------------------------------------------------------------------------
@@ -344,7 +363,10 @@ async fn unknown_agent_errors() {
     let aid = AgentId::from_uuid(Uuid::from_u128(99));
     let (inspector, _seen) = FakeInspector::new(
         true,
-        InspectResult::Ok(ConversationDetails { last_topic: None, token_count: None }),
+        InspectResult::Ok(ConversationDetails {
+            last_topic: None,
+            token_count: None,
+        }),
     );
 
     let uc = InspectConversation::new(