Implement terrain symbol generation profiles

BUILDING.txt

@@ -75,9 +75,9 @@ All required GameTests should pass before distributing a build.
 
 GameTests use `build/gametest-run/world`, separate from the normal development
 world. Gradle starts each default run with a fresh world and removes it after
-a successful run. Failed worlds are retained under
-`build/gametest-run/failed-worlds/` for inspection until the next successful
-run. Logs and configuration are kept. A caller-supplied `-PgameTestRunDir`
+every run, whether tests pass or fail. The GameTest server always uses seed `0`,
+so retries regenerate a clean world with that seed. Logs and configuration are kept.
+A caller-supplied `-PgameTestRunDir`
 is never removed automatically.
 
 To run the suite in a fresh temporary directory instead, use: