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/features/memory/MemoryPanel.tsx

@@ -18,6 +18,7 @@ import { useCallback, useState } from "react";
 import type { MemoryIndexEntry } from "@/domain";
 import { Button, Panel, Spinner } from "@/shared";
 import { useGateways } from "@/app/di";
+import { useEmbedder } from "@/features/embedder";
 import { MemoryEditor } from "./MemoryEditor";
 import { useMemory } from "./useMemory";
 
@@ -31,6 +32,7 @@ type EditorState = { mode: "create" } | { mode: "edit"; entry: MemoryIndexEntry
 
 export function MemoryPanel({ projectId }: MemoryPanelProps) {
   const vm = useMemory(projectId);
+  const embedderVm = useEmbedder();
   const { memory } = useGateways();
 
   const [editorState, setEditorState] = useState<EditorState | null>(null);
@@ -87,6 +89,22 @@ export function MemoryPanel({ projectId }: MemoryPanelProps) {
       )}
 
       <Panel title="Memory" className="flex flex-col gap-0">
+        {/* ── Active recall tier (read-only transparency) ── */}
+        <p
+          className="border-b border-border px-4 py-2 text-xs text-faint"
+          data-testid="memory-tier"
+        >
+          Tier:{" "}
+          {embedderVm.active ? (
+            <span className="text-content">
+              Vector — {embedderVm.active.strategy}
+              {embedderVm.active.model ? ` ${embedderVm.active.model}` : ""}
+            </span>
+          ) : (
+            <span className="text-content">Naïve (None)</span>
+          )}
+        </p>
+
         {vm.error && (
           <p
             role="alert"

frontend/src/features/memory/memory.test.tsx

@@ -18,7 +18,7 @@
 import { describe, it, expect, vi } from "vitest";
 import { render, screen, waitFor, fireEvent } from "@testing-library/react";
 
-import { MockMemoryGateway } from "@/adapters/mock";
+import { MockMemoryGateway, MockEmbedderGateway } from "@/adapters/mock";
 import type { GatewayError } from "@/domain";
 import type { Gateways } from "@/ports";
 import { DIProvider } from "@/app/di";
@@ -28,7 +28,10 @@ const PROJECT_ID = "proj-memory-test";
 
 function renderMemoryPanel(memory?: MockMemoryGateway) {
   const mem = memory ?? new MockMemoryGateway();
-  const gateways = { memory: mem } as unknown as Gateways;
+  const gateways = {
+    memory: mem,
+    embedder: new MockEmbedderGateway(),
+  } as unknown as Gateways;
   return {
     memory: mem,
     ...render(