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/pty_bridge.rs

@@ -47,7 +47,10 @@ fn send_output_delivers_bytes_to_registered_channel() {
     bridge.register(session, capturing_channel(Arc::clone(&sink)));
 
     let delivered = bridge.send_output(&session, vec![104, 105]);
-    assert!(delivered, "send_output should return true for a live session");
+    assert!(
+        delivered,
+        "send_output should return true for a live session"
+    );
 
     let captured = sink.lock().unwrap();
     assert_eq!(captured.as_slice(), &[vec![104, 105]]);
@@ -82,10 +85,17 @@ fn register_same_session_twice_replaces_channel() {
 
     bridge.register(session, capturing_channel(Arc::clone(&first)));
     bridge.register(session, capturing_channel(Arc::clone(&second)));
-    assert_eq!(bridge.active_sessions(), 1, "same id is replaced, not added");
+    assert_eq!(
+        bridge.active_sessions(),
+        1,
+        "same id is replaced, not added"
+    );
 
     bridge.send_output(&session, vec![9]);
-    assert!(first.lock().unwrap().is_empty(), "old channel no longer used");
+    assert!(
+        first.lock().unwrap().is_empty(),
+        "old channel no longer used"
+    );
     assert_eq!(second.lock().unwrap().as_slice(), &[vec![9]]);
 }
 
@@ -116,7 +126,11 @@ fn unregister_if_is_a_noop_for_a_superseded_generation() {
     bridge.unregister_if(&session, old_gen);
 
     // The current channel survives and still delivers — no duplication, no drop.
-    assert_eq!(bridge.active_sessions(), 1, "live re-attach must not be removed");
+    assert_eq!(
+        bridge.active_sessions(),
+        1,
+        "live re-attach must not be removed"
+    );
     assert!(bridge.send_output(&session, vec![7]));
     assert_eq!(new.lock().unwrap().as_slice(), &[vec![7]]);
 }