[BUG]: registry field without a scope should be respected

### What is the current behavior?

npm_translate_lock (using bzlmod extensions) only appears to parse the registry field in the .npmrc file if it has a scope, ie
```
@myorg:registry=https://somewhere-else.com/myorg
```
but if the field `registry` is set without a scope, it is ignored.
```
registry=https://somewhere-else.com/myorg
```

### Describe the feature

The registry field without a a scope should be parsed and used for all node_modules packages, except when overridden by a scope specific registry

```
registry=https://somewhere-else.com/myorg
```

Start by locating the npm_translate_lock implementation and the .npmrc parsing path used by its bzlmod extension. Trace how scoped registry entries are handled, then verify that an unscoped registry applies to packages without a scope while scoped entries still override it. Done means the reported configuration is respected.

Written by the indexing model from the issue text.