chore: Bump Rust to 1.89 (#35788)

Release Notes:

- N/A

---------

Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/agent2/src/templates.rs

@@ -33,6 +33,10 @@ pub trait Template: Sized {
     }
 }
 
+#[expect(
+    dead_code,
+    reason = "Marked as unused by Rust 1.89 and left as is as of 07 Aug 2025 to let AI team address it."
+)]
 #[derive(Serialize)]
 pub struct GlobTemplate {
     pub project_roots: String,

crates/agent2/src/tools/glob.rs

@@ -19,6 +19,10 @@ struct GlobInput {
     glob: SharedString,
 }
 
+#[expect(
+    dead_code,
+    reason = "Marked as unused by Rust 1.89 and left as is as of 07 Aug 2025 to let AI team address it."
+)]
 struct GlobTool {
     project: Entity<Project>,
     templates: Arc<Templates>,