Update benchmark examples to podio link naming

[Copilot]

The benchmark examples were still reading the old podio association branches, which no longer match the current data model. This left the examples pointing at Associations.* and recID/simID fields while the generated event data exposes link collections with *_Links_from.index and *_Links_to.index.

• Changes
  • Updated the C++ examples to read the link collections instead of the deprecated association branches.
  • Switched the association index arrays to unsigned int and moved to the current *_Links_from / *_Links_to naming convention.
  • Reworded the inline comments to describe the link-based relationship model that matches the ROOT tree layout.

TTreeReaderArray<unsigned int> rec_id = {tree_reader, "_ReconstructedChargedParticleLinks_from.index"};
TTreeReaderArray<unsigned int> sim_id = {tree_reader, "_ReconstructedChargedParticleLinks_to.index"};

• Scope
  • Applied in both the episode source and the learner copy so the benchmark instructions stay aligned with the current EICrecon output format.

• Fixes Transition from Associations to Links #10

[github-actions]

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[wdconinc]

Not sure why the duplication of uchannelrho.cxx, but this seems like a fine change. The benchmark is also not actually in any of the benchmark repositories...

[Copilot]

Pull request overview

Updates the uchannelrho.cxx benchmark example(s) to follow the current podio “Links” branch naming in the ROOT event tree, replacing the deprecated “Associations” branches so the tutorial matches current EICrecon output.

Changes:

• Switched the example’s association/relationship branches from ReconstructedChargedParticleAssociations.* / *_Associations_* to "_ReconstructedChargedParticleLinks_{from,to}.index".
• Standardized the link index reader types to unsigned int.
• Updated inline comments (episode copy) to describe the link-based relationship model.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
learners/files/uchannelrho.cxx	Updates the reader branch names to *_Links_{from,to}.index in the learner copy.
episodes/files/uchannelrho.cxx	Updates branch names and clarifies comments describing how link indices map between reco and MC collections.

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[wdconinc]

Looks all good to me now.

[sjdkay]

Seems fine to me too.