Replace the four capture modes with item/track/master scope actions. Each infers
its range (razor-else-time) and enforces FX scope via non-destructive
FX-bypass-around-render (RAII I_FXEN snapshot/restore over ancestors + master).
Corrects the defect of items captured through parent FX.
Four wet capture actions route to OfflineRenderBackend (snapshot/restore
RENDER_*, 32-bit float), produce a Sample, add to the bank, persist. Pure
render_settings maps source mode to RENDER_SETTINGS and parses P_RAZOREDITS
(tested). No arrange insertion. True dry deferred to M10.
daniel