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/infrastructure/src/pty/mod.rs

@@ -256,9 +256,7 @@ impl PtyPort for PortablePtyAdapter {
         live.writer
             .write_all(data)
             .map_err(|e| PtyError::Io(e.to_string()))?;
-        live.writer
-            .flush()
-            .map_err(|e| PtyError::Io(e.to_string()))
+        live.writer.flush().map_err(|e| PtyError::Io(e.to_string()))
     }
 
     fn resize(&self, handle: &PtyHandle, size: PtySize) -> Result<(), PtyError> {
@@ -313,10 +311,7 @@ impl PtyPort for PortablePtyAdapter {
 
         // Ask the child to terminate, then wait for its real status.
         let _ = live.child.kill();
-        let status = live
-            .child
-            .wait()
-            .map_err(|e| PtyError::Io(e.to_string()))?;
+        let status = live.child.wait().map_err(|e| PtyError::Io(e.to_string()))?;
 
         // Dropping master/writer closes the PTY; the reader thread then sees EOF.
         // Dropping the broadcast hub drops every subscriber's sender, so any