[PWGDQ] Add post-prefilter single-track QA task and fill electron-leg DCA for electron-muon pairs

[Shunsuke-Kurita]

This PR adds two small, related extensions for prefilter-aware analysis in the DQ framework.

1. New task AnalysisPostPrefilterTrackSelection in dqEfficiency_withAssoc.cxx

The new task joins ReducedTracksAssoc with the BarrelTrackCuts andPrefilter decisions and fills track-level histogram classes for both surviving(TrackBarrelPostPrefilter_<cut>) and vetoed (TrackBarrelPrefilterVetoed_<cut>) tracks,per track cut and per MC signal.

Use cases:

• direct MC measurement of the photonic electron tagging efficiency, eps_eff = vetoed / (vetoed + survived), per pT bin, needed for residual photonic background corrections;
• post-prefilter per-origin DCA templates for HF-electron template fits (removes the pre/post-prefilter mismatch of the photonic template);
• general prefilter QA at the single-track level.

Implementation notes:

• The prefilter bit positions are resolved from the track-selection cut list viagetTaskOptionValue, in the same way as in AnalysisPrefilterSelection.
• processSkimmed, processSkimmedWithCov and processDummy process functions are provided; the task is off by default (processDummy) and does not affect existingworkflows.

2. Fill electron-leg DCA variables in FillPair for kElectronMuon pairs

VarManager::FillPair fills the leg DCA variables (kDCAxy1/kDCAz1) only for kDecayToEE. This PR fills them also for kElectronMuon (barrel electron leg), guarded by the ReducedTrackBarrel fill map, so that electron-muon pairing tasks can book leg-DCA histograms (e.g. electron pT vs DCAxy for HF-electron studies with the muon condition applied). Not filled in FillPairME, since the mixed-event barrel track type carries no DCA columns (noted in a comment).

[github-actions]

O2 linter results: ❌ 229 errors, ⚠️ 758 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for 6db7649 at 2026-07-29 16:29:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 61 errors and 0 warnings.'
Found 61 errors and 0 warnings.
++ [[ 61 -gt 0 ]]
++ cat /sw/BUILD/20f005e69da19282fabf65f07892576b709f881b/O2Physics-code-check/errors.txt
PWGDQ/Core/VarManager.h:1205:10: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1206:10: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1566:10: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1570:10: error: do not declare C-style arrays, use 'std::array' instead [modernize-avoid-c-arrays,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1801:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1820:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1876:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1900:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1924:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1950:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:1963:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2630:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2766:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2782:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2806:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2852:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2872:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:2930:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3363:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3397:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3425:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3457:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3491:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3545:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3641:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3666:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3941:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:3999:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4051:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4110:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4184:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4436:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4506:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4681:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:4771:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5168:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5229:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5452:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5716:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5821:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:5917:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
PWGDQ/Core/VarManager.h:6025:14: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
[0 more errors; see full log]

Full log here.