Add zoom steps and a larger start caption to the game link (#266)

The released game only ever zoomed in whole steps up to 400%, so a
small camera on a large screen stayed far smaller than it could be.
The "Click to play" caption was drawn in the 11 px panel title size
and was easy to miss.

- GAME_SCALE_STEPS gains 300%, 500% and 600%. The game tab picker,
  Auto in the editor and the game link all read the same list.
- The start caption takes its size from the new Theme.captionSize
  (16) instead of a constant in GameScreen.
- The player page keeps the default arrow cursor at all times. It no
  longer switches to the hand over the caption.

Tests:
- view.test: Auto for 320x180 in 2000x2000 is now 6, with cases
  for 3 and 5. play-settings.test takes 2.5 and 8 as invalid steps.
- e2e 60 checks the caption against the panel title size and the
  arrow cursor before and after the start. Module 03 follows the new
  step list.
- ./check.sh 2808 tests, CHECK EXIT 0 (before the last Theme tweak,
  which changes no test). Full e2e run ALL PASSED, 1574 checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/model/playSettings.ts

@@ -12,7 +12,7 @@ export const DEFAULT_PLAY_FROM: PlayFrom = 'start';
 /** How the game view sizes the camera frame: a fixed factor, the largest step that fits, or fitted. */
 export type GameScale = 'auto' | 'fit' | number;
 
-export const GAME_SCALE_STEPS = [0.25, 0.5, 1, 2, 4];
+export const GAME_SCALE_STEPS = [0.25, 0.5, 1, 2, 3, 4, 5, 6];
 
 export const DEFAULT_GAME_SCALE: GameScale = 1;