[woodruffw]

Fold the global PAX update check into the logical reader test. Retain the first physical extension across a second global header that replaces the same keyword. The next member sees the replacement, and the retained extension still exposes the original value.

This removes a unit test that compared the address of the global-state slot across an update.

Ran cargo test --locked -p tar-framing --lib global.

[codspeed]

Merging this PR will not alter performance

✅ 28 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing ww/pax-update-test (80ee808) with ww/check-member-policy (5bb5d5d)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩