Tests: tighten Bluesky handle normalization assertion

[RCowles]

Summary

• Strengthen the leading-@ Bluesky connect test so it proves the normalized handle is passed to the authorize flow.
• Assert the intercepted authorize URL contains alice.bsky.social and excludes both raw and URL-encoded @alice forms.

Testing

• composer run-script test-php -- --filter test_handle_connect_strips_leading_at
• composer run-script lint-php

[Copilot]

Pull request overview

Tightens the PHPUnit coverage around Bluesky handle normalization in the admin connect flow by asserting that a submitted leading-@ handle is normalized before being used in the upstream authorize/handle-resolution request.

Changes:

• Updates the test_handle_connect_strips_leading_at test to assert the intercepted authorize/handle-resolution URL includes the normalized handle value.
• Adds explicit negative assertions to ensure neither the raw @alice… form nor the URL-encoded %40alice… form is passed through.