add blocked-string rewrite validation fixtures #55

Job	Run time
spec-kit-conformance	43s
wrapper-cross-platform (macos-latest)	43s
test (stable)	26s
wrapper-cross-platform (windows-latest)	1m 51s
test (1.22.x)	18s
wrapper-cross-platform (ubuntu-latest)	36s
	4m 37s

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