Watch: snapshot tests render the complication and multi-select screenshots

ImageRenderer draws the real views with demo data, since the watch simulator
is not drivable here. README covers the widget target and how to add it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

watch/project.yml

@@ -19,6 +19,8 @@ targets:
     platform: watchOS
     sources:
       - WristCode
+      # The complication's views, so the snapshot tests can render them.
+      - WristCodeWidget/WaitingView.swift
     dependencies:
       # Embedded in the watch app's PlugIns folder.
       - target: WristCodeWidget