R1:5963c4c9e06d

Fix history link in Diffusion non-root browse views

Summary:
Fixes T9798. That task has good repro instructions.

In sub-views, we don't link the "History" icon correctly -- we only link it to `history/README` instead of `history/path/to/README`. Add the full path.

Also canonicalize the paths in a slightly prettier and more consistenty way.

Test Plan: Viewed root and non-root browse tables, saw links show up properly.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9798

Differential Revision…