Grant meter credits over MCP

Draft
ST
16d ago
+2555-78

Stacked on #15423.

Makes the credits endpoint easy to find over MCP. Agents find tools by searching their descriptions, so this rewrites the endpoint's description to match how people ask, "Grant free units (credits) on a customer's usage meter, for example to compensate for an outage or reward an action."

Also regenerates the spec, SDKs and client, and adds the tool to the MCP docs.

Open questions:

  • Does gram use the 2027-01 API version?
  • Do we need to add a tool description somewhere else in gram?