Add persistent business compute seller demo

[Abiorh001]

Summary

Adds a business-facing OmniClaw seller example under examples/business-compute/.

This is a real business web app surface, not a CLI seller surface. The business integrates OmniClaw directly through the seller backend APIs for x402 requirements and verification,
while buyers pay real x402 URLs through OmniClaw.

What this adds

• paid compute products
• paid compute session products with credits
• paid research-paper PDF products
• direct seller-side OmniClaw backend integration
• signed post-payment PDF download URLs
• Redis-backed persistence for business state
• launcher script for the full local demo

Behavior now supported

• unpaid access returns 402 Payment Required
• buyer pays the business URL through OmniClaw
• seller unlocks only after verification/settlement
• compute returns real computed output
• paper purchase returns a signed download_url
• direct unauthenticated PDF download is blocked
• compute session purchase returns:
  • session_id
  • submit_url
  • status_url
• session jobs execute and decrement credits
• sessions, job history, settlements, metrics, and event logs survive business app restarts

Files added

• examples/business-compute/README.md
• examples/business-compute/app.py
• examples/business-compute/compute_job.py
• examples/business-compute/papers/machine-commerce-settlement-design.pdf
• examples/business-compute/papers/policy-controlled-agent-finance.pdf
• scripts/start_business_compute_demo.sh

Verified

• direct compute purchase
• compute session purchase
• session job execution
• paid paper unlock
• protected PDF download
• Redis-backed restart persistence

Notes

This example is intentionally business-first:

• the business owns the API surface
• OmniClaw provides the payment and control layer underneath
• seller behavior is not presented as another agent using omniclaw-cli