Require mpi-extensions prefix for MPI builds #1732

Job	Run time
ci-scope	4s
pre-commit / pre-commit	2m 9s
pre-commit / link-check	-1s
ubuntu / gcc-build (ubuntu-26.04, Debug)	51s
windows / msvc-build (Release)	1m 47s
mac / clang-build (Release)	3m 17s
mac / clang-build (Debug)	2m 33s
ubuntu / gcc-build (ubuntu-26.04, Release)	47s
windows / clang-build	3m 40s
ubuntu / clang-build (ubuntu-26.04)	1m 6s
windows / msvc-build (Debug)	4m 11s
ubuntu / gcc-test	0s
ubuntu / gcc-test-extended	0s
ubuntu / clang-sanitizer-build	-1s
ubuntu / clang-test	-1s
ubuntu / clang-test-extended	-1s
ubuntu / clang-sanitizer-test	-1s
ubuntu / gcc-build-codecov	-1s
ubuntu / clang-sanitizer-test-extended	-1s
mac / clang-test	1m 55s
windows / clang-test	1m 24s
windows / msvc-test	2m 3s
windows / clang-test-extended	1m 23s
mac / clang-test-extended	0s
windows / msvc-test-extended	1m 46s
pages	0s
perf	0s
	28m 49s

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