feat(sandbox): add built-in grep and glob tools (#1784)

* feat(sandbox): add grep and glob tools

* refactor(aio-sandbox): use native file search APIs

* fix(sandbox): address review issues in grep/glob tools

- aio_sandbox: use should_ignore_path() instead of should_ignore_name()
  for include_dirs=True branch to filter nested ignored paths correctly
- aio_sandbox: add early exit when max_results reached in glob loop
- aio_sandbox: guard entry.path.startswith(path) before stripping prefix
- aio_sandbox: validate regex locally before sending to remote API
- search: skip lines exceeding max_line_chars to prevent ReDoS
- search: remove resolve() syscall in os.walk loop
- tools: avoid double get_thread_data() call in glob_tool/grep_tool
- tests: add 6 new cases covering the above code paths
- tests: patch get_app_config in truncation test to isolate config

* Fix sandbox grep/glob review feedback

* Remove unrelated Langfuse RFC from PR

.gitignore

@@ -54,4 +54,5 @@ web/
 # Deployment artifacts
 backend/Dockerfile.langgraph
 config.yaml.bak
-.playwright-mcp
+.playwright-mcp
+.gstack/