Add phasespace based forced pid for Far-Backward particles.

[simonge]

Briefly, what does this PR introduce?

Adds an algorithm which recovers the PID of particles detected in certain directions. The Low-Q2 electrons are the only charged particles which can be reconstructed within ~12mrad of the negative z-axis, currently this information isn't included in reconstructed particles.

The same approach could to a certain degree be used for the Far-Forward protons.

This is a temporary alternative to pursing the larger changes required by #1571 where the reconstructed particles from the tagger would come from a different collection.

What kind of change does this PR introduce?

• Bug fix (issue #__)
• New feature (issue #__)
• Documentation update
• Other: __

Please check if this PR fulfills the following:

• Tests for the changes have been added
• Documentation has been added / updated
• Changes have been communicated to collaborators

Does this PR introduce breaking changes? What changes might users need to make to their code?

No

Does this PR change default behavior?

Tags Far-Backward reconstructed particles as electrons.

[github-actions]

Capybara summary for PR 1894

• rec_dis_10x100_minQ2=0_craterlake
• rec_dis_10x100_minQ2=1000_craterlake_tracking_only
• rec_dis_18x275_minQ2=0_craterlake_18x275
• rec_dis_18x275_minQ2=1000_craterlake_18x275
• rec_dis_5x41_minQ2=0_craterlake_5x41
• rec_e_1GeV_20GeV_craterlake
• rec_pi_1GeV_20GeV_craterlake
  ^{_{Last updated 2025-06-03T20:45-04:00 804e4ea}}