Fix intermittent CoreServices XPC crash in RCTBlobManager blob name derivation

[1337mus]

Summary

The crash

-[NSURLResponse suggestedFilename] derives a filename from the response's MIME type. Under the hood, that call makes a CoreServices/UTType XPC round-trip, and that XPC call crashes intermittently when invoked off the main thread (NSXPCEncoder / objc_msgSend frames).

Why it fires on every request

RCTBlobManager.handleNetworkingResponse: calls suggestedFilename on the networking / TurboModule queue for every response it converts to a blob. Since whatwg-fetch reads every response body as a blob, the fragile call runs for every fetch() an app makes. Even a very low per-call crash rate becomes a steady stream of native crashes at scale.

We hit this in production at Phantom (millions of iOS users). Crash stacks consistently point into the UTType XPC machinery under suggestedFilename, always on the networking queue.

The fix

Derive the blob's name from the URL's last path component instead. No XPC involved.

// before
@"name" : RCTNullIfNil([response suggestedFilename]),

// after
@"name" : RCTNullIfNil(response.URL.lastPathComponent),

Tradeoff: filenames from a Content-Disposition header (or a MIME-derived extension) are no longer used. A response blob's name is rarely consumed; it only feeds Blob / File.name for response bodies. If you'd prefer to keep Content-Disposition support, parsing that header directly here would also avoid the XPC call. Happy to iterate.

Related: the same XPC fragility on the upload path was reported in #35096.

Changelog:

[IOS] [FIXED] - Fix intermittent native crash (CoreServices/UTType XPC) in RCTBlobManager when deriving blob names for network responses

Test Plan

• This exact change has run in production at Phantom since May 2026 (applied as a patch). The crash class disappeared and stayed gone.
• Fetch/blob flows (file and image downloads, uploads, WebSocket blobs) are covered by our device-farm e2e suites and are green with this change.
• name is still populated from the URL path, and is empty when the URL has no path component, which matches one of suggestedFilename's own fallback tiers.

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[1337mus]

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[1337mus]

@SamChou19815 @javache @cipolleschi mind taking a look at this one?

[meta-codesync]

@christophpurrer has imported this pull request. If you are a Meta employee, you can view this in D117876442.