Revert "very preliminary implementation of cross-entity community search, switches to correct side panel for feed page"

This reverts commit e3f4390cd4f5ed41b5c95413212cb4fcf88b1b02.
previous commit undid e3f4390cd4f5ed41b5c95413212cb4fcf88b1b02, to temporarily mute the search work. this one reinstates the sidebar changes that were contained in that commit.