7a450ca5ce
When hrr_dim=1 the prefixed float32 blob (4+4=8 bytes) collides in size with a raw float64 blob (1×8=8 bytes), making the format discriminator in bytes_to_phases ambiguous — a legacy blob starting with HRR1 would be misread as a prefixed float32 vector. - phases_to_bytes now accepts an optional dim and falls back to writing raw float64 when the two blob sizes are equal. - bytes_to_phases prefers the legacy float64 interpretation when sizes collide and dim is provided, since phases_to_bytes never writes a prefixed float32 blob at dim=1. - Three regression tests cover dim=1 write, round-trip, and the legacy-prefix collision case. Addresses hermes-sweeper review on PR #30499.