fix: suppress ExperimentalWarning, PEP 668 guidance, setup help

- All 5 CLI bins: shebang --disable-warning=ExperimentalWarning
- Remove NODE_OPTIONS injection from thread.ts spawn (redundant now)
- Bootstrap pip install: venv (recommended) / pipx / source options
- setup --help mentions interactive wizard mode
- Update shebang test to accept -S flag

Fixes #116

packages/agent-mock/src/cli.ts

@@ -1,4 +1,4 @@
-#!/usr/bin/env node
+#!/usr/bin/env -S node --disable-warning=ExperimentalWarning
 
 // eslint-disable-next-line -- dynamic import for version
 const pkg = await import("../package.json", { with: { type: "json" } });