Document where relay_script (SWML) calls are logged; add note to Compatibility API docs

[briankwest]

Problem

After switching a number's call_handler from laml_webhooks to relay_script, subsequent calls stop appearing in the Compatibility API call log (GET /api/laml/2010-04-01/Accounts/{project}/Calls.json). SWML calls are not LaML calls, so this is by design — but nothing in the Compatibility API docs says so, and nothing points to where SWML/Relay calls ARE recorded. A developer watching their telemetry silently disappear after following the SWML setup path has no thread to pull.

Fix

1. Note in the Compatibility API Calls documentation: calls handled by relay_script do not appear in this collection, with a link to where they are recorded.
2. Document the Relay-side call log location/endpoint for SWML calls.
3. Mention on the SWML quickstart/number-configuration pages.