* fix: use localStorage for auth token to enable multi-tab usage
sessionStorage is tab-scoped, so manually opened second tabs cannot
access the auth token delivered via URL fragment to the first tab.
localStorage is shared across all tabs on the same origin, and since
each GSD instance binds to a unique random port the origin already
scopes the token to that instance.
Also adds a `storage` event listener so already-open tabs pick up
token changes immediately.
Closes#2714
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* test: update web-auth-token test for localStorage migration
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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