Rename exec_wait tool to wait (#14983)

Summary
- document that code mode only exposes `exec` and the renamed `wait`
tool
- update code mode tool spec and descriptions to match the new tool name
- rename tests and helper references from `exec_wait` to `wait`

Testing
- Not run (not requested)

codex-rs/core/src/tools/spec.rs

@@ -772,7 +772,7 @@ fn create_write_stdin_tool() -> ToolSpec {
     })
 }
 
-fn create_exec_wait_tool() -> ToolSpec {
+fn create_wait_tool() -> ToolSpec {
     let properties = BTreeMap::from([
         (
             "cell_id".to_string(),
@@ -2597,7 +2597,7 @@ pub(crate) fn build_specs_with_discoverable_tools(
         builder.register_handler(PUBLIC_TOOL_NAME, code_mode_handler);
         push_tool_spec(
             &mut builder,
-            create_exec_wait_tool(),
+            create_wait_tool(),
             /*supports_parallel_tool_calls*/ false,
             config.code_mode_enabled,
         );