🧹 Refactor uf2 tests to remove unsafe unwrap()

[undivisible]

🎯 What:
Replaced unwrap() calls on slice to array conversions (try_into()) with the ? operator in the tests inside in-cli/src/native_emit/uf2.rs. The test function signatures were updated to return Result<(), Box<dyn std::error::Error>>.

💡 Why:
Using unwrap() can lead to unexpected panics, making tests fail ungracefully. Updating the code to use robust error handling via ? is standard practice and improves the overall maintainability and safety of the test suite.

✅ Verification:

1. Formatted code with cargo fmt.
2. Linted code with cargo clippy --all-targets --features extended --locked -- -D warnings.
3. Ran module specific tests via cargo test native_emit.
4. Ran full test suite via cargo test.
5. Ran integration test suite via IN_TEST_SKIP_SWIFT=1 ./install.sh && ~/.local/bin/in test. All test results verified successfully.

✨ Result:
The test suite is now safer and more idiomatic. Code health issues related to unsafe unwrap() usage in these test functions are fully resolved without any regressions in functionality.

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PR created automatically by Jules for task 3432215088667041043 started by @undivisible

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Note

Low Risk
Test-only changes in UF2 encoding tests with no production code or runtime behavior impact.

Overview
Refactors UF2 encoder unit tests in uf2.rs so slice-to-array conversions use ? instead of unwrap(), and the two affected tests return Result<(), Box<dyn std::error::Error>> with Ok(()) on success.

Behavior and assertions are unchanged; this is test-only ergonomics and panic avoidance on conversion failures. The rejects_empty test is untouched.

^{Reviewed by Cursor Bugbot for commit d9cebc5. Configure here.}

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