## What
npm allows `repository` and `bin` in `package.json` to be either an
object or a plain string (npm docs:
[repository](https://docs.npmjs.com/cli/v11/configuring-npm/package-json#repository),
[bin](https://docs.npmjs.com/cli/v11/configuring-npm/package-json#bin)).
The npm registry creator modeled `repository` as a struct and `bin` as
`map[string]string`, so publishing a package whose `package.json` uses
the string form failed with:
```
json: cannot unmarshal string into Go struct field PackageMetadataVersion.PackageMetadata.versions.bin of type map[string]string
```
## Fix
`modules/packages/npm/creator.go`: add `UnmarshalJSON` to `Repository`
(string → `URL`) and a `Bin` type with `UnmarshalJSON` (string → a
single command named after the package, per npm semantics), mirroring
the existing `License` / `User` string-or-object handling. The stored
`Metadata` field types are unchanged.
`bundledDependencies` as a boolean (also noted in #38235) is left out of
scope — it is rare and semantically different (`true` = bundle all
deps).
## Test
`TestParsePackage/ValidRepositoryAndBinAsString` parses a package with
string `repository` and `bin`: it fails on `main` with the error above
and passes with this change. The full `modules/packages/npm` suite is
green and `gofmt` is clean.
Fixes#38235
_AI disclosure: prepared with AI assistance; I reviewed and verified it
(reproduction + tests) and can explain and defend the change._
d392fb1438