agent: Add several UX improvements (#29828)

Still a work in progress.

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Cole Miller <m@cole-miller.net>
Co-authored-by: Nathan Sobo <1789+nathansobo@users.noreply.github.com>
Co-authored-by: Cole Miller <53574922+cole-miller@users.noreply.github.com>

crates/project/src/project.rs

@@ -318,6 +318,13 @@ pub struct ProjectPath {
 }
 
 impl ProjectPath {
+    pub fn from_file(value: &dyn language::File, cx: &App) -> Self {
+        ProjectPath {
+            worktree_id: value.worktree_id(cx),
+            path: value.path().clone(),
+        }
+    }
+
     pub fn from_proto(p: proto::ProjectPath) -> Self {
         Self {
             worktree_id: WorktreeId::from_proto(p.worktree_id),