Fix MSVC build: replace ET_UNWRAP with manual error check

[kirklandsign]

Summary:
ET_UNWRAP uses GCC statement expressions ({...}) which MSVC does not
support, causing compilation failure on Windows CI.

Replace with equivalent manual check: get the Result, check ok(), return
error on failure, then dereference. Same semantics, cross-platform compatible.

Differential Revision: D100218870

[pytorch-bot]

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⏳ 37 Pending, 1 Unrelated Failure

As of commit 2b8e8cd with merge base c5e917d ():

BROKEN TRUNK - The following job failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-samsung-models-linux / linux-job (gh) (trunk failure)
  test_w2l_fp16

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[meta-codesync]

@kirklandsign has exported this pull request. If you are a Meta employee, you can view the originating Diff in D100218870.

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[Copilot]

Pull request overview

This PR fixes Windows/MSVC compilation by removing use of ET_UNWRAP (which relies on GCC/Clang statement-expressions) and replacing it with an equivalent, explicit Result check in the LLM runner metadata path.

Changes:

• Replace ET_UNWRAP(module->get(...)) with auto get_result = ...; if (!get_result.ok()) return get_result.error(); to preserve error-propagation semantics on MSVC.
• Keep metadata extraction behavior the same while making the implementation cross-platform.

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