Optional supersampling (SSAA) for the viewport, adaptive and capped to the texture limit (#1288) (#1321)

* Optional supersampling (SSAA) for the viewport, adaptive and within the texture limit (#1288)

Preferences ▸ Graphics ▸ Supersampling: Off (default), 1.5× or 2×. The frame is drawn into
textures of the viewport's own kind (format, depth/stencil, MSAA) at that multiple of its pixels,
over transparent black, then filtered down into the viewport with four bilinear taps (the exact
2 × 2 box at 2×) and composited premultiplied over the background. Lines keep their on-screen
width; silhouettes and edges come out smoother.

Adaptive (on by default): the view is drawn at full speed while the camera moves and
supersampled once it has held still for a quarter of a second.

The supersampled size stays within the device's largest texture side (#869) and a 384 MiB
budget for colour and depth (MSAA samples included); under 1.25× is not worth it and the frame
is drawn as usual.

Labels in en/de/ja/ko/zh; `ui.prefs` `supersampling` and `supersampling_adaptive`.

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

* Supersampling: factor and adaptive on one row; Off reads Off (1×)

The Graphics page grew past the colour vision menu in the preferences scenario, and a second
Off on the page took its click.

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

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

assets/locales/ja.json

@@ -327,6 +327,10 @@
   "ui.animation": "アニメーション",
   "ui.animation_speed": "アニメーション速度",
   "ui.anti_aliasing": "アンチエイリアス",
+  "ui.supersampling": "スーパーサンプリング (SSAA)",
+  "ui.supersampling_off": "オフ (1×)",
+  "ui.supersampling_adaptive": "ビューが静止しているときのみ",
+  "settings.supersampling_note": "ビューを高い解像度で描画してから縮小します。4K 未満の画面でエッジ、線、グリッドが滑らかになります。GPU の負荷が増えます（1.5× で約 2.25 倍、2× で 4 倍のピクセル）。",
   "ui.display_quality": "表示品質",
   "ui.display_quality_coarse": "粗い",
   "ui.display_quality_normal": "標準",