Pandora bugfix - Shower merging algorithm

[aliciavr]

Reordering of the shower merging algorithm to avoid inconsistent state of PFParticles (-1 track scores).

Description

Please provide a detailed description of the changes this pull request introduces.

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$${\color{blue}\bf{\textrm{IMPORTANT UPDATE Feb 2nd 2026:}}}$$ If you are making a PR which is intended as a patch for the CURRENT production for gen 2 SBND analyses, you must make two PRs: one for develop and one for the production/sbnd-gen2 branch.

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Checklist

• Added at least 1 label from available labels.
• Assigned at least 1 reviewer under Reviewers,
• Assigned all contributers including yourself under Assignees
• [] Linked any relevant issues under Developement
• Does this PR affect CAF data format? If so, please assign a CAF maintainer (PetrilloAtWork or JosiePaton) as additional reviewer.
• Does this affect the standard workflow?
• Is this PR a patch for the ongoing production? If so, separate PR must also be made for production/v10_06_00 branch!

Relevant PR links (optional)

Does this PR require merging another PR in a different repository (such as sbnanobj/sbnobj etc.)?

Link(s) to docdb describing changes (optional)

Is there a docdb describing the issue this solves or the feature added?

[henrylay97]

@aliciavr @AndyChappell I took the liberty of fixing the merge conflict present in this branch (as the base was behind develop, specifically behind the revert PR from last night).

Please take a look again at whether you are happy with this.

The diff should now show the expected diff - the re-inclusion of the ShowerMergingPfoMopUp alg in the correct position with respect to the NeutrinoProperties alg. The diff is now identical to that in PR#908 as expected.

EDIT: Following offline conversations, its worth producing a clean branch without the merge commit necessary.

[henrylay97]

We'll update this branch after the sim reco meeting to ensure a clean commit history