fix(auth): add automatic browser redirect to signInWithSSO

[mandarini]

Summary

Fixes #1848 by adding automatic browser redirect behavior to signInWithSSO, making it consistent with signInWithOAuth.

Problem

When using signInWithSSO, the redirectTo option was being correctly sent to the backend but ignored on the client side. Unlike signInWithOAuth, which automatically redirects users to the provider's authorization page in browser environments, signInWithSSO only returned the URL without performing the redirect.

This inconsistency meant that:

• Users had to manually handle the redirect themselves
• The redirectTo parameter appeared to be ignored
• The API was inconsistent with other OAuth-based authentication methods

Changes

1. Added automatic browser redirect logic to signInWithSSO method (GoTrueClient.ts:1338-1341)

   • Automatically navigates to the SSO provider URL when running in a browser
   • Only redirects when skipBrowserRedirect is not explicitly set to true
   • Uses the same pattern as signInWithOAuth and other OAuth methods

2. Added skipBrowserRedirect option to SignInWithSSO type (lib/types.ts:789-794, 806-811)

   • Allows developers to opt-out of automatic redirect when needed
   • Provides consistency with other authentication methods
   • Maintains full backward compatibility

3. Added test for the new option (GoTrueClient.test.ts:3103-3120)

   • Verifies the skipBrowserRedirect option is properly accepted
   • Documents expected behavior in browser environments

[coveralls]

coverage: 95.276% (+13.5%) from 81.727%
when pulling 008271f on fix/1848-sso-redirectto-ignored
into 5a3820d on master.