UI: turn the editor into a sequential optical layout table

[dragonleopardpig]

Summary

This PR improves the UI editor for sequential optical layouts and fixes several issues in the Object = Infinity workflow.

Main changes

• make the element table editable with a constrained element-type selector
• preserve the sequential optical layout model in the editor
• protect special rows from invalid reordering:
  • Object
  • Image
  • the first real element when the object is at infinity
• fix solver behavior for the image plane so the solved value is the relative image thickness
• keep the finite image plane tied to the table state instead of silently replacing it with a solved back focal distance
• fix plotting/runtime issues around infinity-object mode:
  • first lens remains at physical position 0
  • object arrow is drawn at the first negative x tick
  • that tick is relabeled to −∞
  • incoming collimated rays originate from that object-side tick
  • image position / image thickness / red image arrow stay aligned with the current table state

Result

For infinity-object setups, the display now follows a physically consistent axis model:

• optical elements stay on their real coordinates
• the first lens stays at 0
• the object is represented on the object-side tick labeled −∞
• the image plane shown in the plot and information panel matches the current editor state

Notes

This PR also removes stale display-offset behavior that caused incorrect plotting and runtime errors while editing.

Suggested update comment on the PR:

Updated this PR substantially on the same branch.

The current version focuses on fixing the infinity-object workflow in the editor: the first lens stays at physical position 0, the object is shown on the object-side tick labeled −∞, and the image plane handling now stays aligned with the table state.