PR Summary:

This PR fixes three bugs in the Section Box Navigator tool:

• Replaces Elevation with ProjectElevation throughout, ensuring correct elevation values in linked model / survey-point setups
• Refreshes levels and grids when switching documents
• Disables invalid levels in the dropdown menu (e.g. a "top" level below the current bottom)

Review Summary:

The ProjectElevation substitution is the right fix and is applied consistently across both files. The doc-switch refresh logic is a good addition, but its placement inside the autoupdate guard introduces a regression for users with autoupdate disabled — stale doc, length_unit, grids, and levels will persist after a document switch. The removal of the explicit current_view refresh in btn_align_box_to_view_click is also a latent bug for the same autoupdate-off scenario. One IronPython WPF convention (explicit Nullable<bool> comparison) was flagged per repository standards. A pre-existing type() proxy pattern was noted as a minor code smell while the code is being touched.

Suggestions

• Add a unit test or manual test case covering document switch with autoupdate disabled to catch the stale-globals regression. Apply
• Audit all other button click handlers that reference self.current_view to ensure they refresh via revit.active_view when autoupdate may be off. Apply