gpui: Add support for custom prompt text in PathPromptOptions (#36410)

This will be used to improve the clarity of the git clone UI

### MacOS
<img width="1322" height="128" alt="image"
src="https://github.com/user-attachments/assets/3e511143-12c1-4440-89dd-841b21b2e98e"
/>

### Windows 
<img width="338" height="80" alt="image"
src="https://github.com/user-attachments/assets/766d08d6-0c72-4175-ad24-59dc6188d5f1"
/>

### Linux

<img width="387" height="72" alt="Screenshot From 2025-08-18 15-32-06"
src="https://github.com/user-attachments/assets/3125a7c4-3975-462a-a547-d5d4fac48f22"
/>



Release Notes:

- N/A

crates/gpui/src/platform/linux/platform.rs

@@ -294,6 +294,7 @@ impl<P: LinuxClient + 'static> Platform for P {
                 let request = match ashpd::desktop::file_chooser::OpenFileRequest::default()
                     .modal(true)
                     .title(title)
+                    .accept_label(options.prompt.as_ref().map(crate::SharedString::as_str))
                     .multiple(options.multiple)
                     .directory(options.directories)
                     .send()

crates/gpui/src/platform/mac/platform.rs

@@ -705,6 +705,7 @@ impl Platform for MacPlatform {
                     panel.setCanChooseDirectories_(options.directories.to_objc());
                     panel.setCanChooseFiles_(options.files.to_objc());
                     panel.setAllowsMultipleSelection_(options.multiple.to_objc());
+
                     panel.setCanCreateDirectories(true.to_objc());
                     panel.setResolvesAliases_(false.to_objc());
                     let done_tx = Cell::new(Some(done_tx));
@@ -730,6 +731,11 @@ impl Platform for MacPlatform {
                         }
                     });
                     let block = block.copy();
+
+                    if let Some(prompt) = options.prompt {
+                        let _: () = msg_send![panel, setPrompt: ns_string(&prompt)];
+                    }
+
                     let _: () = msg_send![panel, beginWithCompletionHandler: block];
                 }
             })

crates/gpui/src/platform/windows/platform.rs

@@ -787,6 +787,12 @@ fn file_open_dialog(
 
     unsafe {
         folder_dialog.SetOptions(dialog_options)?;
+
+        if let Some(prompt) = options.prompt {
+            let prompt: &str = &prompt;
+            folder_dialog.SetOkButtonLabel(&HSTRING::from(prompt))?;
+        }
+
         if folder_dialog.Show(window).is_err() {
             // User cancelled
             return Ok(None);