assistant2: Don't suggest thread context for inline assist without a ThreadStore (#23506)

This PR makes it so we don't suggest threads as context in the inline
assist when we don't have a `ThreadStore` to pull from.

Release Notes:

- N/A

crates/assistant2/src/active_thread.rs

@@ -259,7 +259,7 @@ impl ActiveThread {
                         h_flex().flex_wrap().gap_1().px_1p5().pb_1p5().children(
                             context
                                 .into_iter()
-                                .map(|context| ContextPill::new_added(context, false, false, None)),
+                                .map(|context| ContextPill::added(context, false, false, None)),
                         ),
                     )
                 } else {