[ALICE 3] Fix sensitive volumes definition for FT3

[scannito]

Sensitive volume names depend on FT3Base.layoutFT3 and were not correctly fetched for newly introduced layout options.

Additional checks are needed to retrieve the correct sensor ID for digitization.

[Copilot]

Pull request overview

This PR updates FT3 simulation sensitive-volume registration so that sensor volumes are discovered correctly across newly introduced layoutFT3 naming schemes, and adds a volume-id → sensor-id lookup for ProcessHits().

Changes:

• Replace the previous mLayerID-based sensitive-volume identification with an mActiveSensorMap lookup keyed by MC volume ID.
• Redefine defineSensitiveVolumes() to discover sensitive FT3 sensor volumes by iterating over all TGeo volumes and matching known naming signatures for multiple layouts.
• Update FT3 Detector ROOT class version to reflect the data member change.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
Detectors/Upgrades/ALICE3/FT3/simulation/src/Detector.cxx	Reworks sensitive-volume discovery and ProcessHits() volume→sensor mapping.
Detectors/Upgrades/ALICE3/FT3/simulation/include/FT3Simulation/Detector.h	Replaces mLayerID with mActiveSensorMap and bumps ROOT class version.

Comments suppressed due to low confidence (1)

Detectors/Upgrades/ALICE3/FT3/simulation/src/Detector.cxx:660

• When a matching sensitive volume is found, the map stores mActiveSensorMap[volID] = iLayer, which is not sufficient to uniquely identify the sensor for digitization in the presence of multiple directions and/or multiple sensors per layer. Store a unique sensor/chip index here (e.g., include direction and, for segmented volumes, parse and include the sensor/stave indices from the volume name or hierarchy).

          AddSensitiveVolume(v);
          int volID = gMC ? TVirtualMC::GetMC()->VolId(vName.c_str()) : 0;
          if (volID > 0) {
            mActiveSensorMap[volID] = iLayer;
          }

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[alibuild]

Error while checking build/O2/fullCI_slc9 for a8db0f0 at 2026-05-13 18:10:

## sw/BUILD/O2Physics-latest/log
c++: fatal error: Killed signal terminated program cc1plus
ninja: build stopped: subcommand failed.

Full log here.