CI/CD: always run a pull request's own tests

A split step with own: true (split: { files: "**/*.test.{ts,tsx}", own: true }) runs the test files a change adds or changes that no other step's split names. With such a step in runtime.yml, a pull request that adds or changes a test file no step runs (any language: TypeScript and JavaScript, Python, Go, or a Rust crate's files) fails with a tests not run job that lists each file and the reason. Configs without an own step are unchanged.