chore(gate): public-repo PR settings for no-mistakes v1.93

Keep the run intent out of published PR bodies, collapse the generated
appendix, and attribute failing test commands to the change or the base.

Author: dmealing

.no-mistakes.yaml

@@ -59,3 +59,12 @@
 commands:
   test: "scripts/ci-local.sh --only ts-fast --only ts-unit --strict-toolchains"
   lint: "scripts/ci-local.sh --only gates --strict-toolchains"
+
+# Public repository: keep PR bodies short and the run intent out of them.
+pr:
+  publish_intent: false
+  appendix: collapsed
+
+# Mark a failing test command as pre-existing when it also fails on the base.
+test:
+  base_attribution: true