Use GitHub API for pushes by default and require explicit github-token when using custom tokens (#692)

* Ensure `github-token` wins for `git-cli` pushes

* more shenanigans

* Default to GitHub API commit mode

* e2e auth tests

* push missing utils

* rename input

* refactor

* refactor

* refactor

* refactor

* refactor

* refactor

* reuse helpers

* refactor

* refactor

* simplify

* add tests

* refactor

* improve comments

* shift helper

* add comments

* extract test helpers

* update docs and changesets

* update one thing

src/run.test.ts

@@ -99,7 +99,7 @@ const createGithub = (cwd: string) =>
   new GitHub({
     cwd,
     githubToken: "@@GITHUB_TOKEN",
-    commitMode: "github-api",
+    pushWithGitCli: false,
   });
 
 async function initializeGitRepository(cwd: string) {