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/memory_usecases.rs

@@ -17,7 +17,8 @@ use domain::{
 use application::{
     CreateMemory, CreateMemoryInput, DeleteMemory, DeleteMemoryInput, GetMemory, GetMemoryInput,
     ListMemories, ListMemoriesInput, ReadMemoryIndex, ReadMemoryIndexInput, RecallMemory,
-    RecallMemoryInput, ResolveMemoryLinks, ResolveMemoryLinksInput, UpdateMemory, UpdateMemoryInput,
+    RecallMemoryInput, ResolveMemoryLinks, ResolveMemoryLinksInput, UpdateMemory,
+    UpdateMemoryInput,
 };
 
 // ---------------------------------------------------------------------------
@@ -65,10 +66,7 @@ impl MemoryStore for FakeMemories {
         Ok(())
     }
 
-    async fn read_index(
-        &self,
-        _root: &ProjectPath,
-    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+    async fn read_index(&self, _root: &ProjectPath) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
         Ok(self
             .0
             .lock()
@@ -292,7 +290,15 @@ async fn update_revalidates_invariants_and_rejects_empty_content() {
 
     assert_eq!(err.code(), "INVALID");
     // Original note untouched, no event.
-    assert_eq!(store.get(&root(), &slug("note-a")).await.unwrap().body.as_str(), "v1");
+    assert_eq!(
+        store
+            .get(&root(), &slug("note-a"))
+            .await
+            .unwrap()
+            .body
+            .as_str(),
+        "v1"
+    );
     assert!(bus.events().is_empty());
 }