Read SBS before TIME/DATE to latch a coherent snapshot in synchronous
ERTC mode. A rollover between the previous calendar and subsecond reads
could move the tick count backwards and cause false receive timeouts.
Preserve millisecond conversion and shared delta-helper semantics.
Add actual-source rollover, conversion and register-locking coverage.
Leave acquisition limits and RF timing unchanged.
Co-Authored-By: OpenAI coding assistant <noreply@openai.com>
Signed-off-by: nip <182409448+nip-was-here@users.noreply.github.com>