assistant2: Add tiny design improvements (#27399)

Really small stuff, like adding icons and adjusting colors.

Release Notes:

- N/A

crates/assistant2/src/active_thread.rs

@@ -1258,12 +1258,13 @@ impl ActiveThread {
             "edit-files" => IconName::Pencil,
             "fetch" => IconName::Globe,
             "list-directory" => IconName::Folder,
+            "move-path" => IconName::ArrowRightLeft,
             "now" => IconName::Info,
             "path-search" => IconName::SearchCode,
             "read-file" => IconName::Eye,
             "regex-search" => IconName::Regex,
             "thinking" => IconName::Brain,
-            _ => IconName::Terminal,
+            _ => IconName::Cog,
         };
 
         div().py_2().child(

crates/assistant2/src/context_picker.rs

@@ -67,7 +67,7 @@ impl ContextPickerMode {
 
     pub fn label(&self) -> &'static str {
         match self {
-            Self::File => "File/Directory",
+            Self::File => "Files & Directories",
             Self::Fetch => "Fetch",
             Self::Thread => "Thread",
         }

crates/assistant2/src/context_picker/completion_provider.rs

@@ -821,7 +821,7 @@ mod tests {
                     format!("six.txt {}", separator!("dir/b")).as_str(),
                     format!("five.txt {}", separator!("dir/b")).as_str(),
                     format!("four.txt {}", separator!("dir/a")).as_str(),
-                    "File/Directory",
+                    "Files & Directories",
                     "Fetch"
                 ]
             );