fix(types): add missing port property to StartOptions interface

[thecaptain789]

Description

The port configuration property is defined in lib/API/schema.json but was missing from the TypeScript type definitions in types/index.d.ts.

This PR adds the port property to the StartOptions interface to match the runtime behavior documented in the schema.

Schema Reference

From lib/API/schema.json:

"port": {
  "type": "number",
  "docDescription": "Shortcut to inject a PORT environment variable"
}

Changes

• Added port?: number property to StartOptions interface
• Added JSDoc comment matching the schema description

Related Issue

Fixes #6045

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