Leave the full test run to CI

Every push runs the gate, the editor suite and the three games on the Gitea
runner, so a local full run only costs four minutes of waiting.

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

README.md

@@ -810,10 +810,11 @@ full suite takes about four minutes that way. `tools/lib/browser.mjs` therefore
 machine down. (`--use-angle=gl` and `--use-gl=egl` measure cheaper still, but get no WebGL context at
 all, so the app never renders.)
 
-**Run it here by default.** With the GPU in use the full suite costs about four minutes and roughly 0.8 of the
-four cores of this box (60% renderer, 18% GPU process, load ~1.0), which it carries fine. While one
-step is being worked on, `GM_STEPS` keeps a run to seconds – take the whole suite before a commit,
-or when a change touches drawing, the widget toolkit or anything else every step sees.
+**Leave the full run to CI.** Every push runs the whole proof on the runner (see *Continuous
+integration*), so locally take only what the change needs: the gate, plus the step that covers it –
+`GM_STEPS` keeps that to seconds. The whole suite works here too and costs about four minutes and
+roughly 0.8 of the four cores of this box (60% renderer, 18% GPU process, load ~1.0), but four
+minutes of waiting buys nothing the push does not give.
 
 **`./e2e.sh start` runs the suite detached**, in a transient `game-maker-e2e.service`, and returns at
 once; output goes to `logs/e2e-<date>_<time>.log` (gitignored) and ends in `=== E2E EXIT n ===`.