Allow disabling the multi-agent wait tool (#34887)

## What changed

- Add a default-on `features.multi_agent_v2.wait_agent_enabled` setting.
- Omit `collaboration.wait_agent` from the tool plan when the setting is disabled, independently of `features.current_time_reminder.sleep_tool`.

## Testing

- Cover configuration parsing and tool exposure with both clock sleep states.

GitOrigin-RevId: c2f34c5edd5bc191d6a5ac41d7bbb80708da1202

codex-rs/features/src/tests.rs

@@ -412,6 +412,7 @@ multi_agent_mode_hint_text = "Custom mode guidance."
 tool_namespace = "agents"
 hide_spawn_agent_metadata = true
 expose_spawn_agent_model_overrides = true
+wait_agent_enabled = false
 non_code_mode_only = true
 "#,
     )
@@ -437,6 +438,7 @@ non_code_mode_only = true
             tool_namespace: Some("agents".to_string()),
             hide_spawn_agent_metadata: Some(true),
             expose_spawn_agent_model_overrides: Some(true),
+            wait_agent_enabled: Some(false),
             non_code_mode_only: Some(true),
         }))
     );