Improve prompts for tools (#11669)

Improves the descriptions for some of the tools. I wish we had metrics
to back up changes in how the model responds to tool schema changes so
anecdotally I'm just going to say this _seems_ improved.

Release Notes:

- N/A

crates/assistant2/Cargo.toml

@@ -23,6 +23,7 @@ chrono.workspace = true
 collections.workspace = true
 editor.workspace = true
 feature_flags.workspace = true
+file_icons.workspace = true
 fs.workspace = true
 futures.workspace = true
 fuzzy.workspace = true
@@ -43,6 +44,7 @@ story = { workspace = true, optional = true }
 theme.workspace = true
 ui.workspace = true
 util.workspace = true
+unindent.workspace = true
 workspace.workspace = true
 
 [dev-dependencies]