fix(ios): open custom schemes instead of always reporting failure

[CodyPChristian]

The problem

Browser.Open gates UIApplication.open behind canOpenURL:

if UIApplication.shared.canOpenURL(url) {
    UIApplication.shared.open(url, options: [:]) { opened in ... }
} else {
    semaphore.signal()   // success stays false
}

For a custom scheme, iOS answers canOpenURL false unless that scheme is listed in the calling app's LSApplicationQueriesSchemes — regardless of whether anything on the device handles it.

So Browser::open('myapp://') returns false on a phone that has myapp installed, and there's no way to tell that apart from a real failure.

That's awkward for any app that declares its target schemes up front, and impossible for one that can't. In our case a host app opens a per-tenant companion app whose scheme is issued long after the host's Info.plist is written — so the guard reports "nothing can open this" for every custom scheme, permanently.

The change

Drop the guard and let open's completion handler report the result.

It already answers the same question, without the declaration requirement, and answers it from what actually happened rather than from a pre-flight guess. That makes success mean what the docblock says it means: "True if successfully opened."

Why this shouldn't regress anything

• http/https is unaffected. canOpenURL is unconditionally true for those — no declaration needed — so the guard never rejected one. That's every example in the README.
• No new failure mode. UIApplication.open with a scheme nothing handles doesn't throw; the completion handler receives false, which is exactly what the else branch was producing.
• The only behavior that changes is for custom schemes, which currently always fail.

The 2s semaphore timeout is untouched; the failure path now costs one async round-trip instead of returning immediately, which isn't observable.

Testing

vendor/bin/pest — 58 passed, 129 assertions, unchanged.

The Swift isn't covered by that suite. Verified by building a real app against the branch: it compiles, launches, and the custom-scheme path now reaches open instead of short-circuiting.

Also added a short note to the README's open() section, since custom schemes weren't mentioned and the success return is how you detect the target app isn't installed.

[simonhamp]

Good call