[PWGDQ] Add variable names and units for all FIT detector variables

Add fgVariableNames and fgVariableUnits definitions for all 35 FIT
detector variables, following the same pattern as ZDC variables:

- FT0 variables: amplitude (a.u.), time (ns), trigger mask, fired channels
- FDD variables: amplitude (a.u.), time (ns), trigger mask, fired channels
- FV0A variables: amplitude (a.u.), time (ns), trigger mask, fired channels
- Pileup flags: BB/BG flags for FT0A/C, FV0A, FDDA/C (dimensionless)
- BC distances: TOR, TSC, TVX, V0A, T0A (in BC units)

This completes the FIT variable definition infrastructure in VarManager,
enabling histogram creation and analysis with proper axis labels and units.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: minjungkim12

PWGDQ/Core/VarManager.cxx

@@ -499,6 +499,72 @@ void VarManager::SetDefaultVarNames()
   fgVariableUnits[kTimeZPA] = "";
   fgVariableNames[kTimeZPC] = "ZPC time";
   fgVariableUnits[kTimeZPC] = "";
+  fgVariableNames[kAmplitudeFT0A] = "FT0A amplitude";
+  fgVariableUnits[kAmplitudeFT0A] = "a.u.";
+  fgVariableNames[kAmplitudeFT0C] = "FT0C amplitude";
+  fgVariableUnits[kAmplitudeFT0C] = "a.u.";
+  fgVariableNames[kTimeFT0A] = "FT0A time";
+  fgVariableUnits[kTimeFT0A] = "ns";
+  fgVariableNames[kTimeFT0C] = "FT0C time";
+  fgVariableUnits[kTimeFT0C] = "ns";
+  fgVariableNames[kTriggerMaskFT0] = "FT0 trigger mask";
+  fgVariableUnits[kTriggerMaskFT0] = "";
+  fgVariableNames[kNFiredChannelsFT0A] = "FT0A fired channels";
+  fgVariableUnits[kNFiredChannelsFT0A] = "";
+  fgVariableNames[kNFiredChannelsFT0C] = "FT0C fired channels";
+  fgVariableUnits[kNFiredChannelsFT0C] = "";
+  fgVariableNames[kAmplitudeFDDA] = "FDDA amplitude";
+  fgVariableUnits[kAmplitudeFDDA] = "a.u.";
+  fgVariableNames[kAmplitudeFDDC] = "FDDC amplitude";
+  fgVariableUnits[kAmplitudeFDDC] = "a.u.";
+  fgVariableNames[kTimeFDDA] = "FDDA time";
+  fgVariableUnits[kTimeFDDA] = "ns";
+  fgVariableNames[kTimeFDDC] = "FDDC time";
+  fgVariableUnits[kTimeFDDC] = "ns";
+  fgVariableNames[kTriggerMaskFDD] = "FDD trigger mask";
+  fgVariableUnits[kTriggerMaskFDD] = "";
+  fgVariableNames[kNFiredChannelsFDDA] = "FDDA fired channels";
+  fgVariableUnits[kNFiredChannelsFDDA] = "";
+  fgVariableNames[kNFiredChannelsFDDC] = "FDDC fired channels";
+  fgVariableUnits[kNFiredChannelsFDDC] = "";
+  fgVariableNames[kAmplitudeFV0A] = "FV0A amplitude";
+  fgVariableUnits[kAmplitudeFV0A] = "a.u.";
+  fgVariableNames[kTimeFV0A] = "FV0A time";
+  fgVariableUnits[kTimeFV0A] = "ns";
+  fgVariableNames[kTriggerMaskFV0A] = "FV0A trigger mask";
+  fgVariableUnits[kTriggerMaskFV0A] = "";
+  fgVariableNames[kNFiredChannelsFV0A] = "FV0A fired channels";
+  fgVariableUnits[kNFiredChannelsFV0A] = "";
+  fgVariableNames[kBBFT0Apf] = "FT0A BB pileup flag";
+  fgVariableUnits[kBBFT0Apf] = "";
+  fgVariableNames[kBGFT0Apf] = "FT0A BG pileup flag";
+  fgVariableUnits[kBGFT0Apf] = "";
+  fgVariableNames[kBBFT0Cpf] = "FT0C BB pileup flag";
+  fgVariableUnits[kBBFT0Cpf] = "";
+  fgVariableNames[kBGFT0Cpf] = "FT0C BG pileup flag";
+  fgVariableUnits[kBGFT0Cpf] = "";
+  fgVariableNames[kBBFV0Apf] = "FV0A BB pileup flag";
+  fgVariableUnits[kBBFV0Apf] = "";
+  fgVariableNames[kBGFV0Apf] = "FV0A BG pileup flag";
+  fgVariableUnits[kBGFV0Apf] = "";
+  fgVariableNames[kBBFDDApf] = "FDDA BB pileup flag";
+  fgVariableUnits[kBBFDDApf] = "";
+  fgVariableNames[kBGFDDApf] = "FDDA BG pileup flag";
+  fgVariableUnits[kBGFDDApf] = "";
+  fgVariableNames[kBBFDDCpf] = "FDDC BB pileup flag";
+  fgVariableUnits[kBBFDDCpf] = "";
+  fgVariableNames[kBGFDDCpf] = "FDDC BG pileup flag";
+  fgVariableUnits[kBGFDDCpf] = "";
+  fgVariableNames[kDistClosestBcTOR] = "Distance to closest BC with TOR";
+  fgVariableUnits[kDistClosestBcTOR] = "BC";
+  fgVariableNames[kDistClosestBcTSC] = "Distance to closest BC with TSC";
+  fgVariableUnits[kDistClosestBcTSC] = "BC";
+  fgVariableNames[kDistClosestBcTVX] = "Distance to closest BC with TVX";
+  fgVariableUnits[kDistClosestBcTVX] = "BC";
+  fgVariableNames[kDistClosestBcV0A] = "Distance to closest BC with V0A";
+  fgVariableUnits[kDistClosestBcV0A] = "BC";
+  fgVariableNames[kDistClosestBcT0A] = "Distance to closest BC with T0A";
+  fgVariableUnits[kDistClosestBcT0A] = "BC";
   fgVariableNames[kMultNTracksHasITS] = "#tracks in PV with ITS";
   fgVariableUnits[kMultNTracksHasITS] = "";
   fgVariableNames[kMultNTracksHasTPC] = "#tracks in PV with TPC";