Retry overtaken cuts at actual CPU progress after older source events have
drained, retaining frame-end and RZX chronology. Use a fixed 35000-tstate
cadence without a runtime setting; document suspension across timeline and
source discontinuities.
Retain partition tests and add real-dispatch ordering regressions plus
compile-time interval builds for deterministic PCM comparisons. Link the
existing string helper from a shared compilation unit rather than duplicating it
in tests.
