Add Vibes-Coded as Solana x402 merchant example — agent reliability APIs + prepaid resume

## Proposed example: Vibes-Coded — Solana x402 agent reliability APIs

### Why this fits AgentCore Payments

AgentCore Payments demos often show Base/EVM merchants. A **Solana USDC** pay-per-call catalog is a useful complementary example for multi-chain agents (same HTTP 402 shape; different `accepts[]` network).

Vibes-Coded runs 100+ Outcome APIs (guards, receipts, research SKUs) with:

- Solana USDC primary (+ optional Base ExactEvm)
- Prepaid resume (`/start` → `X-Vibes-Key`) so agents don’t wallet-sign every hop
- Offline-verifiable `action-receipt` (mint / verify / pubkey)

### Live references

| Piece | URL |
|------|-----|
| Catalog | https://vibes-coded.com/api/v1/outcomes/meta |
| Impulse SKU | `POST …/outcomes/action-receipt` ($0.02) |
| Prepaid fund | https://vibes-coded.com/start |
| Well-known | https://vibes-coded.com/.well-known/x402.json |

### Suggested sample flow

1. `GET/POST` an Outcome → HTTP 402 with Solana `accepts[]`
2. Settle USDC (or use prepaid key) → JSON result
3. Optional: verify `action-receipt` offline with published pubkey

Happy to adapt naming/shape to match other merchant examples in this repo. Public endpoints stay free to call for demos.

Start by reading the repository's existing merchant examples and compare their flow with the linked Vibes-Coded catalog and x402 metadata. Confirm how the Solana payment, prepaid resume key, and optional action-receipt verification should fit the repository's example structure; done means a working example covers the proposed request, payment or prepaid path, and result flow.

Written by the indexing model from the issue text.