Make project search landing page scrollable if too small (#21338)

Address
https://github.com/zed-industries/zed/issues/21317#issuecomment-2508011556


https://github.com/user-attachments/assets/089844fc-a485-44a6-8e8b-d294f28e9ea2

Release Notes:

- N/A

crates/search/src/project_search.rs

@@ -371,6 +371,8 @@ impl Render for ProjectSearchView {
                 .track_focus(&self.focus_handle(cx))
                 .child(
                     v_flex()
+                        .id("project-search-landing-page")
+                        .overflow_y_scroll()
                         .max_w_80()
                         .gap_1()
                         .child(heading_text)