feat: pay Responses WebSocket through Tempo MPP

[gakonst]

Summary

• keep MPP entirely in bin/nanocodex as a CLI-owned loopback WebSocket middleware; no Nanocodex library crate imports MPP, Alloy, Tempo wallet, or SQLite code
• expose direct OpenAI as the default and explicit --provider.openai, plus paid OpenAI-over-Tempo through --provider.tempo and --provider.tempo.* overrides
• load the active Tempo Wallet account and Accounts SDK P-256 access key from ~/.tempo/wallet/store.json; there is no raw-private-key flag or new signer trait
• share ~/.tempo/wallet/channels.db with MPPx and Wallet CLI, bootstrap server session state, reconcile TIP-1034 on-chain state, and continue cumulative vouchers from a cold client
• use alloy-transport-mpp for the HTTP payment probe, WebSocket authorization, in-band voucher requests, application frames, top-ups, and close-ready flow
• apply the same provider configuration and cooperative adapter shutdown to one-shot runs and the TUI
• default to Tempo mainnet and wss://openai.mpp.tempo.xyz/v1/responses

The provider namespace is CLI configuration only. Nanocodex still supports the OpenAI Responses WebSocket model family and the core/service crates remain unchanged.

TIP-1034 and MPPx parity

The CLI pins merged mpp-rs main at 0c509633f9ebc97861ed89d85dbe62798b9bb981. That stack follows current MPPx behavior for:

• channel scope identity: payee, token, escrow, and chain
• explicit escrow override, challenge escrowContract/escrow hints, then the canonical native precompile fallback
• Tempo mainnet as the omitted-chain default
• native TIP-1034 open/top-up transactions and cumulative TIP-1020 vouchers
• unique sponsored repeat top-ups through a randomized past validAfter
• authenticated durable session bootstrap and signed highest-voucher rehydration

Upstream dependencies

• tempoxyz/mpp-rs #316-#326 are merged, including WebSocket transport, proof binding, stores and rehydration, wallet access keys, lifecycle/top-up handling, MPPx bootstrap parity, the generic service client, and TIP-1034 parity
• tempoxyz/mpp-proxy #245 is merged and deployed
• wevm/mppx #675-#677 are merged
• wevm/mppx #688 is green and awaiting review; it applies the same pre-WebSocket top-up behavior to the TypeScript client

Validation

• cargo test -p nanocodex-bin --all-targets: 120 passed
• cargo clippy -p nanocodex-bin --all-targets -- -D warnings
• cargo fmt --all -- --check
• all ten commits on the rebased branch have GitHub-verified SSH signatures

Live mainnet result

The final compiled one-shot CLI loaded the existing Tempo Wallet access key and shared SQLite session, selected gpt-5.6-sol, connected through the local MPP middleware to the hosted OpenAI Responses WebSocket, and returned exactly tip1034-final-ok.

It reused TIP-1034 channel 0xdca07bd5d0808c10e8253a17c8c67192939cfd7045cfe8bf6ed17e63b1754d9b. The persisted cumulative voucher advanced from 650,791 to 728,735 atomic units, so this run paid exactly 77,944 atomic units ($0.077944). The response completed with 8,006 input tokens, 9 output tokens, one connection attempt, zero WebSocket reconnects, and zero response retries.