fix: align orchestration behavior with agent framework docs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ARCHITECTURE.md

@@ -92,10 +92,10 @@ sequenceDiagram
     M->>M: Create run record and mark session running
     M->>S: run-turn command
     S->>C: Execute workflow
-    C-->>S: Partial output / tool activity / handoffs
+    C-->>S: Partial output / tool activity / handoffs / input requests
     S-->>M: Stream deltas and activity events
     M-->>R: Push session events and workspace updates
-    C-->>S: Final messages
+    C-->>S: Final messages or turn boundary
     S-->>M: Completion or error
     M->>M: Finalize run and persist state
     M-->>R: Final workspace snapshot
@@ -134,6 +134,8 @@ Patterns describe how agents collaborate. The architecture supports:
 - handoff flows
 - group chat style collaboration
 
+Their runtime semantics follow the Agent Framework orchestration model: sequential and group chat preserve a visible shared conversation, concurrent aggregates multiple independent responses into one turn, and handoff turns can end once the active agent has responded and is waiting for the next user input.
+
 Patterns are shared application data, not renderer-only configuration. That means the same pattern definition can drive validation, persistence, UI rendering, and sidecar execution.
 
 ### Sessions