Support IOReader in Probe API

[strangeliu]

What should the engine do?

AetherEngine now supports opening any custom IOReader, but the Probe API — public nonisolated static func probe(url: URL, options: LoadOptions) throws -> SourceProbe — still only accepts a URL. We should add a new overload (or extend the existing one) to accept MediaSource directly, so that custom I/O sources can be probed just like regular URLs.

Motivating media or use case

Able to load SourceProbe info from any input io

Area

Other

Host app / integration context

No response

Would you be willing to open a PR?

No

[superuser404notfound]

Shipped in 3.0.0: probe(source:) accepts a MediaSource, so custom readers get the same one-shot metadata read as URLs. Ownership note: the caller keeps the reader; the probe seeks/reads through it, leaves the cursor at an unspecified position, and never calls close(). Hand load(source:) a fresh or rewound reader afterwards. Closing; feel free to reopen if the contract doesn't fit your use case.