Don't panic syncing a browser pane whose navigation failed

[freddysae0]

Opened by Claude (Claude Code), the AI assistant of @freddysae0, on their behalf.

Fixes #62

Problem

On macOS, a browser pane whose navigation fails (an unresolvable host, being offline, a typo in the URL) aborts muxel a few seconds after launch. The pane is restored on every launch, so muxel crash-loops until someone edits workspace.json by hand.

WKWebView.URL becomes nil once a provisional navigation fails. lb-wry's url_from_webview calls .unwrap() on that value. BrowserView::sync runs inside a GPUI task on the main dispatch queue, so the panic can't unwind and the process gets SIGABRT. The existing .url().ok()? never runs, because the panic happens before any Result is produced. Upstream tauri-apps/wry still has the same unwrap.

Fix

sync now goes through a small committed_url helper:

• macOS: checks WKWebView.URL (and its absoluteString) before calling wry::WebView::url(). When there is no URL, sync returns None, the same way it already handles other "nothing to sync yet" states. The next tick tries again.
• Windows: unchanged. WebView2's url() already returns a Result.

There are no behaviour changes for pages that load. One file changed.

Verification

• cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings and cargo test --workspace all pass.
• I reproduced the crash end to end in an isolated HOME. The workspace has a single browser pane, browser_enabled = true, and the build was instrumented with temporary eprintln!s that are not part of this PR:

Build	browser_url	Webview built	sync saw URL == nil	Result
master	https://no-such-host-xyz123.invalid/	yes	n/a	abort after 4–14 s, url_from_webview panic (5/5 runs)
master	https://deploy-preview-17--…netlify.app-/ (the original report)	yes	n/a	abort after 6 s, same panic
this PR	https://no-such-host-xyz123.invalid/	yes	12× and 18×	alive at 25 s (2/2 runs)
this PR	https://deploy-preview-17--…netlify.app-/	yes	10×	alive at 25 s
this PR	https://example.com/	yes	0× (Some("https://example.com/") on every tick)	alive, URL syncs as before

The table only counts runs where the webview was actually created. A few launches from a script never painted the pane, and I left those out because they prove nothing either way.

I built locally without full Xcode, so these binaries used gpui's runtime_shaders feature. That change is local only and not included here.

I also confirmed the nil with a standalone Swift WKWebView probe, with no muxel or wry involved. The URL is set right after load, and is nil about 6 s later for an unresolvable host. For example.com it stays set.

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