Fix per-module channel map slicing in light MC truth generation

adc0 = imod // adc_per_mod * adc_per_mod rounds the module index down as
if it were an ADC index, so every module m > 0 sliced another module's
block of the channel map. The resulting global SiPM indices all fall
below the module's offset, get clamped to -1, and np.take then reads the
last SiPM of the module's light_dat for every cell: each
mc_truth/light_module{m} (m > 0) row holds one SiPM's truth copied into
all adc_per_mod x n_channels cells (verified bitwise against the paired
LARNDSIM light_dat). Module 0 and the single-dataset (2x2) path are
unaffected, as are the waveforms, which are remapped with the full
channel map in next().

Use adc0 = imod * adc_per_mod so each module slices its own rows.

Author: MadivB

src/proto_nd_flow/reco/light/mc_event_generator.py

@@ -218,7 +218,7 @@ def init(self):
         for imod in range(nmod):
             in_name = f'light_dat_module{imod}'
             this_light_dat = self.light_dat[in_name]
-            adc0 = imod // adc_per_mod * adc_per_mod
+            adc0 = imod * adc_per_mod
             this_channel_map = self.channel_map[adc0:adc0+adc_per_mod]
             out_name = f'{self.mc_truth_dset_name}_module{imod}'
             self.data_manager.create_dset(out_name, dtype=this_light_dat.dtype,