zeta_cli: Avoid unnecessary rechecks in retrieval-stats (#39267)

Before this change, it would save every buffer and wait for diagnostics.
For rust analyzer this would cause a lot of rechecking and greatly slow
down the analysis

Release Notes:

- N/A

Co-authored-by: Agus <agus@zed.dev>

crates/edit_prediction_context/src/syntax_index.rs

@@ -35,6 +35,10 @@ use crate::outline::declarations_in_buffer;
 //
 // * Send multiple selected excerpt ranges. Challenge is that excerpt ranges influence which
 // references are present and their scores.
+//
+// * Include single-file worktrees / non visible worktrees? E.g. go to definition that resolves to a
+// file in a build dependency. Should not be editable in that case - but how to distinguish the case
+// where it should be editable?
 
 // Potential future optimizations:
 //