Preserve project filters during repository import and reveal

Import/reveal flows clear the active project filter even when the target remains filtered. Reimplement the filter-preservation path on current main with focused coverage. Source PR: https://github.com/stablyai/orca/pull/12691. Contributor credit: @rmadrazo97. No contributor action requested.

Start by reviewing the source PR at https://github.com/stablyai/orca/pull/12691 and tracing the current import and reveal flows on main. Reimplement the filter-preservation path and add focused coverage showing that an active project filter remains applied when the target is still filtered.

Written by the indexing model from the issue text.