editor: Wrap placeholder if text overflows (#37919)

This fixes an issue where long placeholders would be cut off, e.g. in a
Claude Code thread:

<img width="387" height="115" alt="image"
src="https://github.com/user-attachments/assets/831a54aa-cf2b-4d87-af86-e368a5936f6b"
/>

Now:

<img width="354" height="115" alt="image"
src="https://github.com/user-attachments/assets/e5df5e05-0869-4db2-8dee-38611263191c"
/>


Most of the changes in this PR are caused by us requiring `&mut Window`
in `set_placeholder_text`.

Release Notes:

- Fixed an issue where placeholders inside editors would not wrap

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>

crates/git_ui/src/commit_modal.rs

@@ -198,7 +198,7 @@ impl CommitModal {
             && commit_message.is_empty()
         {
             commit_editor.update(cx, |editor, cx| {
-                editor.set_placeholder_text(suggested_commit_message, cx);
+                editor.set_placeholder_text(&suggested_commit_message, window, cx);
             });
         }