* Add regression test for browser back history
* Fix browser back history handoff
* Fix browser tab favicon not updating on navigation
Two issues caused stale or missing favicons in browser tabs:
1. KVO race: The isLoading observer read webView.isLoading inside a deferred
Task instead of capturing the KVO change value at observation time. For fast
navigations (back-forward cache), isLoading flips true→false before the Task
runs, so handleWebViewLoadingChanged(true) was never called and the old
favicon was never cleared.
2. SPA favicon discovery: Sites that inject <link rel="icon"> via JavaScript
(e.g. React apps) had no favicon link in the DOM when didFinish fired. The
fallback to /favicon.ico often 404'd, leaving the globe icon permanently.
Now retries the JS query after 600ms to give client-side scripts time to
add the tag.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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