Only made some necessary changes:
1. remove `GOEXPERIMENT`, only use jsonv2
1. `make fmt`
* `SigningKey` and `Signature` were affected due to some bugs in the
toolchain, so rewrote them
1. remove or fix fragile magic numbers and strings
* the outputs of image/gzip/zlib packages are different
1. update "nolint" comments for the changed lint behaviors
1. add `tls.MLKEM1024`
When running `golangci-lint` without `GOEXPERIMENT=jsonv2`, a lint error
`import 'encoding/json' is not allowed` is seen.
All other files in the module that import `encodings/json` have
`//nolint` already, so add it.
---
This PR was written with the help of Claude Opus 4.6
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>
