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/orchestrator/service.rs

@@ -16,7 +16,7 @@
 use std::sync::Arc;
 
 use domain::ports::ProfileStore;
-use domain::{OrchestratorCommand, Project, ProfileId};
+use domain::{OrchestratorCommand, OrchestratorVisibility, ProfileId, Project};
 
 use crate::agent::{
     CreateAgentFromScratch, CreateAgentInput, LaunchAgent, LaunchAgentInput, ListAgents,
@@ -95,7 +95,11 @@ impl OrchestratorService {
                 name,
                 profile,
                 context,
-            } => self.spawn_agent(project, name, profile, context).await,
+                visibility,
+            } => {
+                self.spawn_agent(project, name, profile, context, visibility)
+                    .await
+            }
             OrchestratorCommand::StopAgent { name } => self.stop_agent(project, name).await,
             OrchestratorCommand::UpdateAgentContext { name, context } => {
                 self.update_agent_context(project, name, context).await
@@ -115,15 +119,19 @@ impl OrchestratorService {
         &self,
         project: &Project,
         name: String,
-        profile: String,
+        profile: Option<String>,
         context: Option<String>,
+        visibility: OrchestratorVisibility,
     ) -> Result<OrchestratorOutcome, AppError> {
         let existing = self.find_agent_id_by_name(project, &name).await?;
 
         let agent_id = match existing {
             Some(id) => id,
             None => {
-                let profile_id = self.resolve_profile(&profile).await?;
+                let profile = profile.as_deref().ok_or_else(|| {
+                    AppError::Invalid("profile is required to create an agent".to_owned())
+                })?;
+                let profile_id = self.resolve_profile(profile).await?;
                 let created = self
                     .create_agent
                     .execute(CreateAgentInput {
@@ -137,19 +145,54 @@ impl OrchestratorService {
             }
         };
 
+        if let Some(session_id) = self.sessions.session_for_agent(&agent_id) {
+            match visibility {
+                OrchestratorVisibility::Background => {
+                    return Ok(OrchestratorOutcome {
+                        detail: format!("agent {name} already running in background"),
+                    });
+                }
+                OrchestratorVisibility::Visible { node_id } => {
+                    let session = self
+                        .sessions
+                        .rebind_agent_node(&agent_id, node_id)
+                        .ok_or_else(|| {
+                            AppError::NotFound(format!(
+                                "running session {session_id} for agent {name}"
+                            ))
+                        })?;
+                    return Ok(OrchestratorOutcome {
+                        detail: format!("attached agent {name} to cell {}", session.node_id),
+                    });
+                }
+            }
+        }
+
+        let node_id = match visibility {
+            OrchestratorVisibility::Background => None,
+            OrchestratorVisibility::Visible { node_id } => Some(node_id),
+        };
+
         self.launch_agent
             .execute(LaunchAgentInput {
                 project: project.clone(),
                 agent_id,
                 rows: DEFAULT_ROWS,
                 cols: DEFAULT_COLS,
-                node_id: None,
+                node_id,
                 conversation_id: None,
             })
             .await?;
 
         Ok(OrchestratorOutcome {
-            detail: format!("launched agent {name}"),
+            detail: match visibility {
+                OrchestratorVisibility::Background => {
+                    format!("launched agent {name} in background")
+                }
+                OrchestratorVisibility::Visible { node_id } => {
+                    format!("launched agent {name} in cell {node_id}")
+                }
+            },
         })
     }