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/domain/tests/embedder_profile.rs

@@ -105,10 +105,19 @@ fn profile_uses_camel_case_keys_and_skips_none_options() {
     )
     .unwrap();
     let json = serde_json::to_string(&p).unwrap();
-    assert!(json.contains("\"apiKeyEnv\":\"MY_KEY\""), "camelCase apiKeyEnv: {json}");
-    assert!(json.contains("\"strategy\":\"api\""), "camelCase strategy: {json}");
+    assert!(
+        json.contains("\"apiKeyEnv\":\"MY_KEY\""),
+        "camelCase apiKeyEnv: {json}"
+    );
+    assert!(
+        json.contains("\"strategy\":\"api\""),
+        "camelCase strategy: {json}"
+    );
     // `model` is None ⇒ skipped from the wire form.
-    assert!(!json.contains("\"model\""), "None model must be skipped: {json}");
+    assert!(
+        !json.contains("\"model\""),
+        "None model must be skipped: {json}"
+    );
 }
 
 #[test]
@@ -138,7 +147,10 @@ fn none_profile_has_none_strategy() {
     let p = EmbedderProfile::none();
     assert_eq!(p.strategy, EmbedderStrategy::None);
     assert_eq!(p.id, "none");
-    assert!(p.dimension > 0, "even the none profile keeps a non-zero dimension");
+    assert!(
+        p.dimension > 0,
+        "even the none profile keeps a non-zero dimension"
+    );
     // And it round-trips like any other profile.
     roundtrip(&p);
 }
@@ -151,7 +163,9 @@ fn none_profile_has_none_strategy() {
 fn new_rejects_empty_id() {
     assert!(matches!(
         EmbedderProfile::new("", "Name", EmbedderStrategy::None, None, None, None, 8),
-        Err(DomainError::EmptyField { field: "embedder.id" })
+        Err(DomainError::EmptyField {
+            field: "embedder.id"
+        })
     ));
 }
 
@@ -177,7 +191,8 @@ fn new_rejects_zero_dimension() {
 
 #[test]
 fn new_accepts_valid_minimal_profile() {
-    let p = EmbedderProfile::new("id", "Name", EmbedderStrategy::None, None, None, None, 1).unwrap();
+    let p =
+        EmbedderProfile::new("id", "Name", EmbedderStrategy::None, None, None, None, 1).unwrap();
     assert_eq!(p.dimension, 1);
     assert_eq!(p.strategy, EmbedderStrategy::None);
 }