feat: add shell tool call delta message handling

Implemented the buildShellToolCallDeltaMessage function to map client shell output to the delta format for Cursor's terminal bubble. This includes handling both stdout and stderr events. Updated the service to publish these messages when processing execution results. Additionally, added a test for enabling terminal output UI streaming in the bootstrap statsig configuration.

internal/cursor/state_db.go

@@ -30,6 +30,7 @@ const (
 var cursorStateDisabledStatsigGates = []string{
 	"decompose_always_local_ext_host",
 	"cursor_extensions_isolation_v2",
+	"disable_terminal_output_ui_streaming",
 }
 
 // InjectCursorUserInfo synchronizes the Cursor user-level auth cache used by the