Textures: Linear/Nearest labels; prove the filter pass does not resample pixel art (#68)

Dropdown labels are now Linear (default) and Nearest; the stored values
linear/nearest are unchanged, old project files load as before.

e2e 12c-ii measures in Play at camera zoom 1.37 (screen scale 1.434): a
Nearest edge sampled across seven pixels is byte-identical with and without
a neutral Adjust colors shader, and brightness 0.5 on the same path darkens,
so the pass really runs there. New hook __gm.gameRect(id).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

README.md

@@ -37,7 +37,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 720 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 723 checks (GM_STEPS=20 for one step)
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs
 node tools/seed-actor.mjs && node tools/smoke-actor.mjs