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/domain/src/fileguard.rs

@@ -65,7 +65,9 @@ pub enum GuardError {
     /// A party that is **not** the orchestrator attempted to `acquire_write` the
     /// single-writer [`GuardedResource::ProjectContext`]. It must *propose* the
     /// change for validation rather than writing directly.
-    #[error("writing the global project context is reserved to the orchestrator; propose instead")]
+    #[error(
+        "writing the global project context is reserved to its effective writer; propose instead"
+    )]
     Forbidden,
 }