Pin or validate the WhatsApp Baileys version-discovery source

## Summary

The WhatsApp network policy permits a runtime `GET` from the mutable Baileys `master` branch on `raw.githubusercontent.com` so the client can discover protocol-version information.

## Current behavior

- The egress rule is narrowly limited by host, method, and path.
- The permitted path still names a moving branch:
`/WhiskeySockets/Baileys/master/src/Defaults/index.ts`.
- The policy and its regression coverage do not bind the response to an immutable revision or verify its integrity before the value can affect runtime behavior.

## Risk

An upstream branch update can change content consumed inside the sandbox without a corresponding reviewed NemoClaw change. That makes the effective third-party supply-chain input mutable even though the network path is otherwise constrained.

## Desired behavior

Use an immutable reviewed Baileys revision or content-addressed artifact for version discovery. If an immutable source cannot be used, validate the response narrowly enough that unexpected content cannot influence runtime behavior.

## Acceptance criteria

- The runtime version-discovery source is immutable or integrity/format validated.
- The policy remains limited to the minimum required host, method, and path.
- Regression coverage rejects an unexpected or unapproved source/response.
- OpenClaw and Hermes WhatsApp policy variants remain consistent.