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>

frontend/src/adapters/embedder.ts

@@ -0,0 +1,35 @@
+/**
+ * Tauri adapter for {@link EmbedderGateway} (L14 / lot C2). Like the sibling
+ * adapters this is one of the *only* places that calls `invoke()`; components
+ * reach it exclusively through the port.
+ *
+ * Commands use snake_case (Tauri convention); payload keys are camelCase
+ * (matching the backend DTO `#[serde(rename_all = "camelCase")]`). The mutating
+ * command `save_embedder_profile` wraps its field under a `request` key (as
+ * `save_profile` does); `delete_embedder_profile` passes its arg flat.
+ */
+
+import { invoke } from "@tauri-apps/api/core";
+
+import type { EmbedderEngines, EmbedderProfile } from "@/domain";
+import type { EmbedderGateway } from "@/ports";
+
+export class TauriEmbedderGateway implements EmbedderGateway {
+  listEmbedderProfiles(): Promise<EmbedderProfile[]> {
+    return invoke<EmbedderProfile[]>("list_embedder_profiles");
+  }
+
+  saveEmbedderProfile(profile: EmbedderProfile): Promise<EmbedderProfile> {
+    return invoke<EmbedderProfile>("save_embedder_profile", {
+      request: { profile },
+    });
+  }
+
+  async deleteEmbedderProfile(embedderId: string): Promise<void> {
+    await invoke("delete_embedder_profile", { embedderId });
+  }
+
+  describeEmbedderEngines(): Promise<EmbedderEngines> {
+    return invoke<EmbedderEngines>("describe_embedder_engines");
+  }
+}