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/src/embedder/mod.rs

@@ -0,0 +1,24 @@
+//! Embedder configuration use cases (LOT C2 — §14.5.3).
+//!
+//! CRUD over the declarative [`domain::profile::EmbedderProfile`]s
+//! ([`ListEmbedderProfiles`], [`SaveEmbedderProfile`], [`DeleteEmbedderProfile`])
+//! plus a read-only description of the available engines ([`DescribeEmbedderEngines`]):
+//! the recommended local ONNX models, the detected local environment, and which
+//! strategies are actually compiled into this binary.
+//!
+//! A changed embedder takes effect at the **next IDE start** (the composition root
+//! freezes the recall for the session): these use cases only persist/inspect config,
+//! they never reconfigure a live recall.
+
+mod suggestion;
+mod usecases;
+
+pub use suggestion::{
+    CheckEmbedderSuggestion, CheckEmbedderSuggestionInput, CheckEmbedderSuggestionOutput,
+    DismissChoice, DismissEmbedderSuggestion, DismissEmbedderSuggestionInput, SuggestedThisSession,
+};
+pub use usecases::{
+    DeleteEmbedderProfile, DeleteEmbedderProfileInput, DescribeEmbedderEngines,
+    EmbedderEnginesView, ListEmbedderProfiles, ListEmbedderProfilesOutput, OnnxModelView,
+    SaveEmbedderProfile, SaveEmbedderProfileInput, SaveEmbedderProfileOutput,
+};