[PWGLF] Deuteron proton correlation: add ITS cut for purity studies

[ercolessi]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 5 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/code-check for fb8caa8 at 2026-10-01 17:20:

## sw/BUILD/O2Physics-code-check-latest/log
--
========== List of issues found ==========
++ echo 'Found 2 errors and 1 warnings.'
Found 2 errors and 1 warnings.
++ [[ 2 -gt 0 ]]
++ cat /sw/BUILD/d9ca46499d3e2977eed399ae05b5460021c50fa2/O2Physics-code-check/errors.txt
PWGLF/Tasks/Nuspex/hadronnucleicorrelation.cxx:1950:40: error: std::move of the expression of the trivially-copyable type 'value_type' (aka 'GenCoalescenceCandidate') has no effect [performance-move-const-arg,-warnings-as-errors]
PWGLF/Tasks/Nuspex/hadronnucleicorrelation.cxx:1955:38: error: std::move of the variable 'deuteron' of the trivially-copyable type 'GenCoalescenceCandidate' has no effect [performance-move-const-arg,-warnings-as-errors]
++ [[ 1 -gt 0 ]]
++ cat /sw/BUILD/d9ca46499d3e2977eed399ae05b5460021c50fa2/O2Physics-code-check/warnings.txt
PWGLF/Tasks/Nuspex/hadronnucleicorrelation.cxx:1729:22: warning: use designated initializer list to initialize 'GenCandidate' [modernize-use-designated-initializers]
++ [[ 2 -gt 0 ]]
++ exit 1
--

Full log here.

[alibuild]

Error while checking build/O2Physics/staging for fb8caa8 at 2026-10-01 17:22:

No log files found

Full log here.