chore: add web-login proxy doneUrl regression for npm-profile fix

[manzoorwanijk]

Adds a regression test for #8875. The fix is in npm-profile (npm/npm-profile#191).

This test is expected to be red until bundled npm-profile is bumped to the release with the fix, and turns green after that.

Why

npm login --auth-type=web silently fails behind a proxy/mirror: the returned doneUrl points at the canonical registry.npmjs.org instead of the proxy, so npm polls the wrong host, gets a 403, and falls back to couch auth (which also fails). Fixed in npm-profile by rewriting doneUrl to the configured registry origin.

How

• @npmcli/mock-registry: weblogin() gains an optional doneRegistry to emulate a proxy advertising a doneUrl on another origin.
• test/lib/commands/login.js: proxy registry whose doneUrl is on registry.npmjs.org; asserts the token is saved with no couch fallback. Fails with the current bundled npm-profile, passes once it is bumped.

References

Fixes #8875
Depends on: npm/npm-profile#191
Related: #9550

[manzoorwanijk]

@owlstronaut we can update and land this once npm/npm-profile#191 lands in this repo after release and bump.