Fix project and buffer search input width (#21949)

Closes https://github.com/zed-industries/zed/issues/21922

Now, both the project and buffer search inputs have a min-width set so
that text inside it, as well as the additional controls, are always
visible even at the window's smallest possible size, which looks like
this:

<img width="407" alt="Screenshot 2024-12-13 at 00 35 46"
src="https://github.com/user-attachments/assets/e6e2c4c6-4f75-4663-8c65-590e02141a5d"
/>


Release Notes:

- N/A

crates/search/src/buffer_search.rs

@@ -209,6 +209,7 @@ impl Render for BufferSearchBar {
 
         let input_base_styles = || {
             h_flex()
+                .min_w_32()
                 .w(input_width)
                 .h_8()
                 .px_2()

crates/search/src/project_search.rs

@@ -1595,6 +1595,7 @@ impl Render for ProjectSearchBar {
 
         let input_base_styles = || {
             h_flex()
+                .min_w_32()
                 .w(input_width)
                 .h_8()
                 .px_2()