chore: add .gitattributes and update test fixtures #104

Job	Run time
Coverage & contract checks	3m 5s
Quality (Node 22 on ubuntu-latest)	4m 15s
Quality (Node 20 on ubuntu-latest)	4m 9s
Quality (Node 22 on macos-latest)	3m 21s
Quality (Node 24 on ubuntu-latest)	3m 41s
Quality (Node 22 on windows-latest)	7m 12s
Post-pack smoke test	33s
	26m 16s

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