test(ios): reuse ResizingProcessor instead of a second transcoding mock

[jkmassel]

Stacked on #633. Follow-up from an adversarial review of #625.

What?

Deletes TranscodingProcessor and points its one call site at the existing ResizingProcessor. Drops @unchecked Sendable from two stateless mocks.

Why?

TranscodingProcessor was a duplicate of ResizingProcessor — same .processed(_, mimeType: "video/mp4", filename: "clip.mp4") result, one call site — and the weaker of the two on both counts that matter:

• It wrote to a fixed $TMPDIR/clip.mp4 rather than a per-call UUID path inside the managed upload directory. processAndUpload's cleanup defer then deletes that path, so the mock unlinks a process-wide filename it does not own. Verified by planting a sentinel: before: exists=true → after: exists=false.
• It swallowed the write with try? and still returned .processed(<URL>, …). Forcing the write to fail leaves the file absent and all four assertions still pass — the test cannot detect a regression where processing silently produces nothing. ResizingProcessor uses try.

@unchecked Sendable on ThrowingUploader and DecliningProcessor bought nothing — both are stateless final classes that satisfy the conformance on their own. The annotation belongs on the mocks holding NSLock-guarded state; carrying it on stateless ones normalizes it as boilerplate, which is how an unsynchronized property gets added later without a diagnostic.

How?

• ios/Tests/GutenbergKitTests/Media/MediaUploadServerTests.swift: TranscodingProcessor deleted; processesForHostReleasedDelegate uses ResizingProcessor. @unchecked Sendable removed from ThrowingUploader and DecliningProcessor. ContentTypeDeleteClient keeps it — it subclasses an @unchecked Sendable class and must restate the conformance.

Mutation sensitivity is unchanged: against a weakly-held processor the swapped test still fails in all four places with the real symptom (passthroughUploadCalled → true).

Testing Instructions

• swift test — 981 tests, host suite green
• swift build --build-tests — zero warnings in the library and test targets
• SwiftLint clean

Related

Two other findings from the same review are already fixed upstream in this stack: the off-main delegate release (HTTPServer.stop() now clears newConnectionHandler) and the #WeakMutability warning, both in #625.

EditorViewControllerMediaLifetimeTests — vacuous for the same class of reason, since it never loads the editor — has been deleted on #625, where the file lived. That also removed LifetimeProbeDelegate, so the mock cleanup in this PR is the remainder.

[wpmobilebot]

XCFramework Build

This PR's XCFramework is available for testing. Add the following to your Package.swift:

.package(url: "https://github.com/wordpress-mobile/GutenbergKit", branch: "pr-build/637")

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