The revert of story 86's merge left broken code from stories 131/135
that depended on it. Removed dead inline event dispatch (referencing
undefined event_type, pty_writer, PermissionReqMsg), added activity_tx
to process_json_event, and removed unused permission_tx parameter from
chat_stream/chat (permissions go through MCP, not PTY).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>