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/application/tests/git_usecases.rs

@@ -82,11 +82,7 @@ impl GitPort for FakeGit {
         self.record(&format!("checkout:{branch}"));
         Ok(())
     }
-    async fn log(
-        &self,
-        _r: &ProjectPath,
-        _limit: usize,
-    ) -> Result<Vec<GitCommitInfo>, GitError> {
+    async fn log(&self, _r: &ProjectPath, _limit: usize) -> Result<Vec<GitCommitInfo>, GitError> {
         self.record("log");
         Ok(Vec::new())
     }
@@ -135,7 +131,9 @@ async fn status_passes_through_to_port() {
         staged: true,
     }]);
     let out = GitStatus::new(Arc::new(git.clone()))
-        .execute(GitStatusInput { root: ROOT.to_owned() })
+        .execute(GitStatusInput {
+            root: ROOT.to_owned(),
+        })
         .await
         .unwrap();
     assert_eq!(out.entries.len(), 1);
@@ -229,9 +227,14 @@ async fn checkout_publishes_event() {
 #[tokio::test]
 async fn branches_returns_list_and_current() {
     let git = FakeGit::default();
-    git.set_branches(vec!["main".to_owned(), "dev".to_owned()], Some("main".to_owned()));
+    git.set_branches(
+        vec!["main".to_owned(), "dev".to_owned()],
+        Some("main".to_owned()),
+    );
     let out = GitBranches::new(Arc::new(git.clone()))
-        .execute(GitBranchesInput { root: ROOT.to_owned() })
+        .execute(GitBranchesInput {
+            root: ROOT.to_owned(),
+        })
         .await
         .unwrap();
     assert_eq!(out.branches, vec!["main", "dev"]);