PIPE-3250: Support SPW-partitioned SubMS slices in contfile, imaging, and selfcal
- Enforce SubMS SPW isolation in ObservingRun and implement spectral window access methods (spectral_windows, get_spectral_window) on SubMS.
- Update to_local_spw and flag command filtering to preserve real SPW IDs created by mstransform (reindex=False).
- Sanitize ContFileHandler to guard against CASA advisechansel overflow and filter out SPWs not present in the SubMS slice.
- In ImageParamsHeuristics, unwrap representative_target to parent_ms, partition SPW selections per MS in calc_ms_frame_ranges(), and guard sensitivity calculations for non-member SPWs.
- Support SubMS slices in auto_selfcal by dynamically mapping visibilities per SPW and aggregating total effective bandwidth across slices.
- Wrap temporary listobs file removal in try...finally in T2_1DetailsRenderer.
