feat(agents): role orchestrateur du contexte global expose et configurable par agent — isOrchestrator distinct des permissions MCP, DTO update_project_orchestrator (terminologie wire legacy conservee), refus idea_context_update explicite avec writer effectif + orientation idea_context_propose, surface AgentsPanel + adaptateurs frontend — #276 (QA verte: cargo fmt/check, tests cibles application/app-tauri/infrastructure/backend, npm typecheck, 69/69 tests frontend agents/adapters)

crates/app-tauri/src/commands.rs

@@ -32,8 +32,8 @@ use application::{
     UnassignSkillFromAgentInput, UpdateAgentContactableInput, UpdateAgentContextInput,
     UpdateAgentEffortInput, UpdateAgentMcpToolPermissionsInput, UpdateAgentPermissionsInput,
     UpdateAgentSystemPermissionsInput, UpdateMemoryInput, UpdateProjectContextInput,
-    UpdateProjectMcpToolPermissionsInput, UpdateProjectPermissionsInput,
-    UpdateProjectSystemPermissionsInput, UpdateSkillInput,
+    UpdateProjectMcpToolPermissionsInput, UpdateProjectOrchestratorInput,
+    UpdateProjectPermissionsInput, UpdateProjectSystemPermissionsInput, UpdateSkillInput,
 };
 use backend::stream::OutputSink;
 use domain::ports::ModelServerRuntime;
@@ -81,7 +81,8 @@ use crate::dto::{
     UpdateAgentContactableRequestDto, UpdateAgentContextRequestDto, UpdateAgentEffortRequestDto,
     UpdateAgentMcpToolPermissionsRequestDto, UpdateAgentPermissionsRequestDto,
     UpdateAgentSystemPermissionsRequestDto, UpdateMemoryRequestDto, UpdateProjectContextRequestDto,
-    UpdateProjectMcpToolPermissionsRequestDto, UpdateProjectPermissionsRequestDto,
+    UpdateProjectMcpToolPermissionsRequestDto, UpdateProjectOrchestratorRequestDto,
+    UpdateProjectOrchestratorResponseDto, UpdateProjectPermissionsRequestDto,
     UpdateProjectSystemPermissionsRequestDto, UpdateSkillRequestDto, UpdateTemplateRequestDto,
     WriteTerminalRequestDto,
 };
@@ -800,6 +801,27 @@ pub async fn update_agent_contactable(
         .map_err(ErrorDto::from)
 }
 
+/// `update_project_orchestrator` — select the single global project-context writer.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] when ids are invalid, the agent is unknown, or persistence fails.
+#[tauri::command]
+pub async fn update_project_orchestrator(
+    request: UpdateProjectOrchestratorRequestDto,
+    state: State<'_, AppState>,
+) -> Result<UpdateProjectOrchestratorResponseDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    let agent_id = parse_agent_id(&request.agent_id)?;
+    state
+        .update_project_orchestrator
+        .execute(UpdateProjectOrchestratorInput { project, agent_id })
+        .await
+        .map(|out| UpdateProjectOrchestratorResponseDto {
+            orchestrator_agent_id: out.orchestrator.to_string(),
+        })
+        .map_err(ErrorDto::from)
+}
+
 /// `resolve_agent_permissions` — resolve project defaults plus agent override.
 ///
 /// # Errors

crates/app-tauri/src/lib.rs

@@ -262,6 +262,7 @@ pub fn run() {
             commands::update_agent_permissions,
             commands::update_agent_effort,
             commands::update_agent_contactable,
+            commands::update_project_orchestrator,
             commands::resolve_agent_permissions,
             commands::get_project_system_permissions,
             commands::update_project_system_permissions,

crates/app-tauri/tests/dto_agents.rs

@@ -6,7 +6,7 @@ use app_tauri_lib::dto::{
     parse_agent_id, AgentDto, AgentListDto, CellKind, ConversationDetailsDto,
     CreateAgentRequestDto, InspectConversationRequestDto, LaunchAgentRequestDto, LiveAgentListDto,
     TerminalSessionDto, UpdateAgentContactableRequestDto, UpdateAgentContextRequestDto,
-    UpdateAgentEffortRequestDto,
+    UpdateAgentEffortRequestDto, UpdateProjectOrchestratorRequestDto,
 };
 use application::AppError;
 use application::{
@@ -188,6 +188,17 @@ fn update_agent_contactable_request_deserialises_camelcase() {
     assert_eq!(dto.agent_id, Uuid::from_u128(2).to_string());
 }
 
+#[test]
+fn update_project_orchestrator_request_deserialises_compatible_wire_fields() {
+    let raw = json!({
+        "projectId": Uuid::from_u128(1).to_string(),
+        "agentId": Uuid::from_u128(2).to_string()
+    });
+    let dto: UpdateProjectOrchestratorRequestDto = serde_json::from_value(raw).unwrap();
+    assert_eq!(dto.project_id, Uuid::from_u128(1).to_string());
+    assert_eq!(dto.agent_id, Uuid::from_u128(2).to_string());
+}
+
 #[test]
 fn launch_agent_request_deserialises_camelcase() {
     let project_id = Uuid::from_u128(1).to_string();