Remove the Hermes WhatsApp session-path compatibility probe

## Problem Statement

PR #8727 keeps a read-only compatibility probe in `channels status --channel whatsapp` while supported Hermes images can place dashboard-paired credentials under `profiles/dashboard-home` even though gateway startup uses `/sandbox/.hermes/platforms/whatsapp/session`.

The probe reads `platforms.whatsapp.extra.session_path` only for status diagnostics when the durable path has no `creds.json`. It does not configure Hermes and must not become a supported session-storage control.

## Desired Behavior

Remove the compatibility probe after every supported Hermes image uses `/sandbox/.hermes/platforms/whatsapp/session` for both dashboard pairing and gateway startup.

Removal is ready when a newly paired sandbox and a rebuilt sandbox both satisfy these observations without the compatibility field:

1. Dashboard pairing writes `creds.json` under the durable path.
2. Gateway startup reads the same path.
3. `channels status --channel whatsapp` reports the durable session without consulting `platforms.whatsapp.extra.session_path`.
4. The documented remove-and-add repair produces the durable path.

## Constraints and Non-goals

- Preserve existing installations until the supported Hermes image set meets the observations above.
- Do not add another configurable session location.
- Remove the compatibility documentation and its focused assertions with the probe.

## Implementation Idea

Delete the configured-path read and dashboard-profile compatibility branch from the WhatsApp status hook, then update the status tests and command reference. Verify newly paired and rebuilt sandboxes against every supported Hermes image before removal.

Related: #8718 and #8727.

Start with the WhatsApp status hook and its focused status tests, then review the command reference for the compatibility field. Verify newly paired and rebuilt sandboxes across every supported Hermes image: pairing, gateway startup, status reporting, and remove-and-add repair must all use the durable session path without consulting the compatibility setting.

Written by the indexing model from the issue text.