Document simulating a call from a specific phone number

[scott-lowe-vapi]

Description

• Adds a short "Simulate a call from a specific phone number" subsection to the simulations advanced page, under "Set variable values". Customers testing caller-authenticated flows (caller identified by {{customer.number}}, then a tool looks up their account) have asked how to do this more than once, and support needs a page to point them to.
• Shows the API override (targetOverrides.variableValues.customer.number) with one PATCH example and a line on transient scenarios. It's API-only because the Variables tab stores flat text names and values, which can't express the nested customer.number.
• Documents two limits, both checked against the platform code:
  • The override replaces the whole customer variable, so any other customer.* fields the assistant uses must be set too.
  • The override only affects {{customer.number}} template resolution. Simulations never set call.customer, so a tool that reads the caller from the server message payload won't see it.
• Adds a troubleshooting row, "A tool looks up the wrong caller", linking to the new subsection.

Testing Steps

• Run the app locally using fern docs dev or navigate to preview deployment
• Ensure that the changed pages and code snippets work

🤖 Generated with Claude Code

[lightsage-app]

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Docs URL: https://vapi-preview-01a11382-43dd-76d7-a6da-e37df6385a4c.docs.buildwithfern.com
Commit: 9fd6723
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[github-actions]

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