feat: add Prism Network action provider

[akimstacks]

Description

Adds a prism action provider for Prism Network: metered GPU compute an agent pays for per call with USDC on Base over x402. No account and no API key sits between the agent and the machine; the agent reads the price from the 402 response, pays from the wallet it already has, and gets the result in the same request.

Five actions, no new dependencies (the workspace already ships @x402/fetch and @x402/evm):

• get_models (free): the models available for inference and their prices
• run_inference (paid): text generation on a rented GPU
• run_batch (paid): several prompts in one request, one payment, with a per-item audit path
• run_gpu_command (paid): a shell command on a rented GPU
• get_gpu_job (free): poll a submitted job

Prism prices inference by the token cap requested, so a large cap on a large batch is the one way an agent can spend more than it meant to. maxPaymentUsdc (default 1) drops any payment option quoted above the cap before the wallet signs anything. When no GPU is warm the paid endpoints answer with a retry notice and take no payment; the provider reports that as charged: false with the wait in seconds, and treats a 429 the same way, so an agent waits instead of reading a cold pool as a failure.

Tests

16 unit tests alongside the provider; the full typescript suite passes. Proven end to end on Base mainnet through the LangChain example:

Chatbot: typescript/examples/langchain-cdp-chatbot (ViemWalletProvider)
Network: base-mainnet
Setup: gpt-4o, wallet funded with USDC, no Prism account or API key

Prompt: What models can you run on Prism, and what do they cost?

The agent called get_models and listed the available models with their
per-call prices in USDC. No payment was made.

Prompt: Run this prompt on a GPU: "Write a haiku about settlement."

The agent called run_inference, paid over x402, and returned the
completion. Settled on chain in
https://basescan.org/tx/0x080b618555b6b217bb59e44badc22e0689c115638b3eb1254cafe194001a6bba

Prompt: Run these three prompts as one batch.

The agent called run_batch: one payment for the three items, answers
returned with a Merkle root and per-item audit paths. Settled in
https://basescan.org/tx/0x4cc961b9dcbdc9396e71d8f22c8a86d65c7d6ec4763c00a6962ed18cfdaae594

Each settlement was submitted by a different Coinbase facilitator address, which is the check that payment went through CDP rather than through Prism itself.

[cb-heimdall]

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