Consolidate theme radius/shadow props and make rounded utilities responsive

- Remove duplicate roundedness/shadowLevel props (keep radius/shadow)
- Switch globals.css radius scale to proportional (square→pill works)
- Replace rounded-full with rounded-md on theme-driven elements
- Remove banner props from Navigation, drop publishing overlay

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.schema.json

@@ -11,9 +11,7 @@
         "bgColor": "#ffffff",
         "fgColor": "#0a0a0a",
         "mutedColor": "#f5f5f5",
-        "roundedness": "md",
-        "radius": "md",
-        "shadowLevel": "sm",
+        "radius": "sm",
         "shadow": "sm",
         "maxWidth": "xl"
       }
@@ -201,9 +199,7 @@
         "bgColor": "#ffffff",
         "fgColor": "#0a0a0a",
         "mutedColor": "#f5f5f5",
-        "roundedness": "md",
-        "radius": "md",
-        "shadowLevel": "sm",
+        "radius": "sm",
         "shadow": "sm",
         "maxWidth": "xl"
       }