Fetch completed AI job results

Retrieves the full AI output for a completed job. Returns HTTP 400 if the job is not yet completed. Call GET /ai-jobs/{jobId} first to confirm status === "completed".

Result shape varies by jobType:

• explain → { explanation: string }
• troubleshoot → { guidance: string }
• analyze_bottlenecks → { analysis: string, doRecommendation: object|null }
• optimize → { suggestions: string[] }

Authentication: Requires an API key (read scope) or an x402 micro-payment (3 credits — $0.0030 USDC on Base). Pass Authorization: Bearer <key> for API key access, or include a signed x402 payment header with call type ai.results (no account required). x402 callers that paid to create the job carry a wallet-session JWT that is accepted here without a second payment round-trip. Use GET /api/billing/x402/config to discover the live price.