Commit dfd1fae

- `@wordpress/build` (`packages/wp-build`) is a generic build tool used both in Gutenberg and by plugins targeting WordPress Core directly. Avoid Gutenberg-specific changes in it.

- Never invoke WordPress's forked or local CLIs through `npx` (e.g. `npx prettier`, `npx wp-scripts`). WordPress ships its own `wp-prettier` fork, and `wp-scripts` is the bin name of `@wordpress/scripts`. A bare `npx wp-scripts` can resolve to an unrelated third-party package on the public registry, not the local tool. Use the npm scripts instead (`npm run format`, `npm run lint:js`, `npm run lint:css` and so on), which run the binaries from local `node_modules`.

- PHP function and class names are renamed at build time (`gutenberg_*` prefix, `*_Gutenberg` suffix) to avoid conflicts with WordPress Core — the built names, not the source names, are what runs (and what tests must call). See `docs/contributors/code/build-system-function-prefixing.md`.

- Packages with TypeScript dev files split their configs: `tsconfig.build.json` (src only, emits `build-types`) and the default `tsconfig.json` (dev project: tests and stories, `noEmit`, jest types). Packages without dev files keep a single `tsconfig.json` build project, and a few packages deviate (a dev-only project with handwritten declarations, or specialized build projects); see the TypeScript section in `packages/README.md`. Reference a split package by `../<pkg>/tsconfig.build.json` and an unsplit one by `../<pkg>`. `npm run build` never type checks (it emits declarations with `--noCheck`); use `npm run typecheck`, and never add jest types to a build project.

- A rejected `apiFetch` is not always an `Error`: a REST error arrives as a plain object (`{ code, message, data }`), `parse: false` rejects with the `Response` (which carries `status`, not `message`), an aborted request rethrows an `AbortError`, and a handler set via `setFetchHandler` can reject anything. Do not interpolate the rejection into a string (`` `${ error }` `` gives `[object Object]`) or branch on `instanceof Error`. Normalise it to a message before showing the user anything, and supply your own copy when there is none — `ensureError` in `packages/core-data/src/private-actions.js` is the reference implementation, though it is local to that file rather than exported.