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/projects/ProjectsView.tsx

@@ -36,13 +36,16 @@ import { AgentsPanel } from "@/features/agents";
 import { TemplatesPanel } from "@/features/templates";
 import { SkillsPanel } from "@/features/skills";
 import { MemoryPanel } from "@/features/memory";
+import { EmbedderSettings } from "@/features/embedder";
 import { GitPanel, GitGraphView } from "@/features/git";
 import { Button, Input, Panel, Tabs, cn } from "@/shared";
 import { useGateways } from "@/app/di";
+import { ProjectContextPanel } from "./ProjectContextPanel";
 import { useProjects } from "./useProjects";
 
 type SidebarTab =
   | "projects"
+  | "context"
   | "agents"
   | "templates"
   | "skills"
@@ -51,6 +54,7 @@ type SidebarTab =
 
 const SIDEBAR_TABS: { id: SidebarTab; label: string }[] = [
   { id: "projects", label: "Projects" },
+  { id: "context", label: "Context" },
   { id: "agents", label: "Agents" },
   { id: "templates", label: "Templates" },
   { id: "skills", label: "Skills" },
@@ -253,6 +257,14 @@ export function ProjectsView() {
               </div>
             )}
 
+            {/* Project context panel */}
+            {sidebarTab === "context" && active && (
+              <ProjectContextPanel projectId={active.id} />
+            )}
+            {sidebarTab === "context" && !active && (
+              <p className="text-sm text-muted">Open a project to edit context.</p>
+            )}
+
             {/* Agents panel — only rendered when active project exists */}
             {sidebarTab === "agents" && active && (
               <AgentsPanel projectId={active.id} projectRoot={active.root} />
@@ -277,9 +289,12 @@ export function ProjectsView() {
               <p className="text-sm text-muted">Open a project to manage skills.</p>
             )}
 
-            {/* Memory panel */}
+            {/* Memory panel + embedder settings */}
             {sidebarTab === "memory" && active && (
-              <MemoryPanel projectId={active.id} />
+              <div className="flex flex-col gap-4">
+                <MemoryPanel projectId={active.id} />
+                <EmbedderSettings />
+              </div>
             )}
             {sidebarTab === "memory" && !active && (
               <p className="text-sm text-muted">Open a project to manage memory.</p>