feat: add get_call_details tool

[nickrobin]

Summary

The existing get_call tool returns a summary projection (id, status, endedReason, assistantId, phoneNumberId, customer.number, scheduledAt) — there's no way to fetch transcripts, recordings, messages, costs, or analysis through MCP without dropping out to the REST API.

This adds a sibling get_call_details tool that returns the full call payload. It accepts an optional include array so callers can scope the response to specific fields and keep LLM context windows manageable on long calls.

Changes

• New schemas in src/schemas/index.ts:
  • GetCallDetailsInputSchema (callId + optional include)
  • CallDetailsOutputSchema (extends CallOutputSchema)
  • CALL_DETAIL_FIELDS constant
• New transformer transformCallDetailsOutput in src/transformers/index.ts — falls back to call.artifact[field] when the field isn't on the top-level call object
• New tool registration get_call_details in src/tools/call.ts, paired with the existing get_call
• E2E test updated to assert the tool is registered

Test plan

• npm run build passes
• tsc --noEmit clean
• Manually verify against a real call ID via the MCP inspector
• include: ['transcript'] returns just { id, transcript }
• No include returns the full summary + all detail fields