assistant2: Allow adding directories as context that contain non-UTF8 files (#26135)

We would previously return an error if there was at least one non-UTF8
file. Now we just ignore them and only add text files. If no text files
are found we show an error.

Release Notes:

- N/A

crates/assistant2/src/context_store.rs

@@ -208,13 +208,19 @@ impl ContextStore {
             let mut text_tasks = Vec::new();
             this.update(&mut cx, |_, cx| {
                 for (path, buffer_entity) in files.into_iter().zip(buffers) {
-                    let buffer_entity = buffer_entity?;
+                    // Skip all binary files and other non-UTF8 files
+                    if let Ok(buffer_entity) = buffer_entity {
                         let buffer = buffer_entity.read(cx);
-                    let (buffer_info, text_task) =
+                        let (buffer_info, text_task) = collect_buffer_info_and_text(
-                        collect_buffer_info_and_text(path, buffer_entity, buffer, cx.to_async());
+                            path,
+                            buffer_entity,
+                            buffer,
+                            cx.to_async(),
+                        );
                         buffer_infos.push(buffer_info);
                         text_tasks.push(text_task);
                     }
+                }
                 anyhow::Ok(())
             })??;