Correctly handle file links in markdown and agent threads (#56024)

Closes https://github.com/zed-industries/zed/issues/54840

There are likely more places we can use this new workspace function in,
but these are the known ones to me right now

Release Notes:

- Fixed file hyperlinks in the agent panel not opening files when
clicked

Co-authored-by: saberoueslati <saberoueslati12@gmail.com>
de744e744cLukas Wirth committed on 6/5/2026, 11:17:44 AM· committed by GitHubparent8807ac4
10 files changedLine totals unavailable