fix: switch system prompt to avoid malformed tool_calls (#650)

* fix: switch system prompt to avoid malformed tool_calls

* fix: circular dependency issue and configurable tool-call style

* fix: regExp issue

packages/core/src/tools/tool-names.ts

@@ -0,0 +1,23 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Tool name constants to avoid circular dependencies.
+ * These constants are used across multiple files and should be kept in sync
+ * with the actual tool class names.
+ */
+export const ToolNames = {
+  EDIT: 'edit',
+  WRITE_FILE: 'write_file',
+  READ_FILE: 'read_file',
+  READ_MANY_FILES: 'read_many_files',
+  GREP: 'search_file_content',
+  GLOB: 'glob',
+  SHELL: 'run_shell_command',
+  TODO_WRITE: 'todo_write',
+  MEMORY: 'save_memory',
+  TASK: 'task',
+} as const;