docs(coding-agent): clarify sandbox example alternative to bash override (#2663)

packages/coding-agent/examples/extensions/sandbox/index.ts

@@ -5,6 +5,10 @@
  * restrictions on bash commands at the OS level (sandbox-exec on macOS,
  * bubblewrap on Linux).
  *
+ * Note: this example intentionally overrides the built-in `bash` tool to show
+ * how built-in tools can be replaced. Alternatively, you could sandbox `bash`
+ * via `tool_call` input mutation without replacing the tool.
+ *
  * Config files (merged, project takes precedence):
  * - ~/.pi/agent/sandbox.json (global)
  * - <cwd>/.pi/sandbox.json (project-local)