### Why?
Should come up with better solution that does not block PRs with git
conflict
x-ref:
https://vercel.slack.com/archives/C02CDC2ALJH/p1785263902728189?thread_ts=1785263687.502649&cid=C02CDC2ALJH
### How?
- Delete `errors.json`, the error-code SWC plugin, generated WASM, merge
driver, and validation/build tooling.
- Stop attaching error codes to server-rendering digests, redboxes, and
telemetry; native `Error.code` and `Error.name` remain available where
applicable.
- Remove the development-overlay error feedback UI, middleware, and
telemetry event that depended on stable codes.
- Update fixtures, snapshots, and guidance for code-free errors and
numeric-only digests.
<!-- NEXT_JS_LLM -->
This update introduces a custom `swc-plugin` for Next.js that appends a
non-enumerable `__NEXT_ERROR_CODE` property to all `Error` instances,
enabling anonymous telemetry while keeping error codes hidden from
console logs. The plugin manages error codes through an append-only
`/packages/next/errors.json` file, which is automatically updated during
the `pnpm build` process using a two-pass system to ensure consistent
error mapping, even during concurrent builds.
Jiwon Choi