Flaky test 903FA85A (1D Bubbles 2 Fluids): No such file 'p0' under -j 48 #1968

Summary

The CPU test 903FA85A (1D -> Bubbles -> 2 Fluid(s)) fails intermittently under high test parallelism with

[Errno 2] No such file ... 'p0'

It passes when run alone (--only 903FA85A).

Context

• Full CPU suite on LLNL Tuolumne: ./mfc.sh test --no-mpi --no-gpu -j 48, with 711 passed, 1 failed (this test), 50 skipped.
• The missing path is the post-process output directory. toolchain/mfc/test/test.py reads silo_hdf5/p0 around line 834, so this looks like a race between a test's post-processing and the harness reading or cleaning its output, or a shared path between concurrently running cases.
• Not investigated further.

Found with Claude Code during a full-suite run for #1963.