chore: applied formatting to all files

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes 🛠 Repo: Files are inconsistently formatted with Prettier #5492
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Consists of two main commits:

1. c65e3a9: Switches the format:prettier task to apply to all files, properly .prettierignores ones we don't want to format, and adds formatting enforcement to CI
2. 4db34cc: Runs npm run format:prettier -- --write

If we wanted to, we could preserve the commits from this PR and add 4db34cc to a .git-blame-ignore-revs file. I'm personally slightly against that because that would add yet another new root-level file to the repo, which makes it just a little more daunting to read through. I would have even preferred to not add another Prettier config file here. Sigh.

🤎

[mark-wiemer]

Looks good as-is, but bonus points if we also upgrade prettier to 3.6.2 (pinning exact version, not ^3.6.2, Prettier does not follow semver) and remove most of the Prettier rules in package.json:

// current rules vs defaults in Prettier 3.6.2
// https://prettier.io/docs/options
  "prettier": {
    "arrowParens": "avoid", // defaults to `always`
    "bracketSpacing": false, // defaults to `true`
    "endOfLine": "auto", // defaults to `lf`
    "singleQuote": true, // defaults to `false`
    "trailingComma": "none" // defaults to `all`, works only on Node v8+ and any browser supporting ES2017
    // suggest keeping this the same to be safe
  },

I think the defaults are better than our customizations in all these scenarios.

Again, happy to approve and merge this one without changes, but the way I see it, if we're going to change formatting, let's do it all in one go to minimize the Git history bloat.

Definitely do NOT want .git-blame-ignore-revs, agree there are already too many top-level files. I've researched it and found these two issues to help us get rid of .prettierignore in the future:

• Add support for ignorePath configuration option prettier/prettier#8192
• config option to ignore paths prettier/prettier#4708

Not much traction on either of them though, but we can always do the work ourselves ;) (very low priority from me!)