Viewer polish, cursor fix, Grok rename + W/S fix, Composer G teleport

Site:
- Cursor follower fades out over iframes (it froze on top of running
  artifacts since iframes swallow pointer events) and when the pointer
  leaves the window
- HTML viewer: full-bleed width on xl screens (up to 90rem), height
  capped to 100dvh-10rem so the frame plus its action row always fits
  the viewport (big iframes ate wheel events and trapped page scroll),
  fullscreen button (overlay + footer action), and Run now auto-aligns
  the frame below the fixed header

Artifacts:
- grok-build: W/S were inverted against the forward vector (W walked
  backward); model label renamed to Grok Build
- composer-2-5: added G-key cycle teleport to its three generated
  landmarks (elven tower, dragon temple, sky ruins) with a start-screen
  hint - they were previously only reachable on foot; ground landmarks
  arrive 10 blocks out facing the structure, sky ruins land on the deck

Run notes updated accordingly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

outputs/grok-build/mythos-craft.html

@@ -1177,8 +1177,8 @@
         );
 
         let moveX = 0, moveZ = 0;
-        if (this.keys['KeyW']) moveZ -= 1;
-        if (this.keys['KeyS']) moveZ += 1;
+        if (this.keys['KeyW']) moveZ += 1; // fix: W/S were inverted — `forward` already points where the camera looks, so W must add +forward (it walked backward before)
+        if (this.keys['KeyS']) moveZ -= 1;
         if (this.keys['KeyA']) moveX -= 1;
         if (this.keys['KeyD']) moveX += 1;