feat(lucid): scoped STRK payment adapter + session-key operational wallet reference

[omarespejel]

Summary

Create a scoped Lucid integration issue that can be executed immediately after release-gate blockers are green.

Goal

Provide a concrete Lucid adapter/reference for Starknet-native paid entrypoints using:

• STRK payment path (x402-starknet flow)
• session-key operational wallet pattern
• reproducible end-to-end example docs

Why

Issue #265 asks for concrete status and examples. Today integration is still WIP; this issue defines the exact deliverable so work can start without ambiguity once security gates are closed.

Dependencies (must be green first)

• P0 Release Gate (No-Backend): ERC-8004 + Agent Account production readiness #273 release gate
• P0-proxy: HMAC + mTLS + nonce replay protection (Redis TTL) #219 proxy auth + replay protection
• contracts: add session signature v2 (SNIP-12) verification path with strict domain separation #255 session signature v2 (SNIP-12 path)
• ci/spec: add shared conformance vectors for session signing v1+v2 across 3 repos #256 tri-repo conformance vectors

Scope

In scope

1. Add Lucid adapter skeleton + wiring docs for Starknet payment path.
2. Provide a STRK paid-tool example flow with request/receipt traceability.
3. Document session-key operational wallet pattern for Lucid agent runtime.
4. Include security notes (trust boundaries, signer mode, replay assumptions).

Out of scope

1. Mainnet production rollout in this issue.
2. Replacing signer proxy boundary or changing contract interfaces.
3. Multi-framework support beyond Lucid in this ticket.

Acceptance Criteria

1. A minimal Lucid example can run against Sepolia and trigger a paid STRK tool path.
2. Session-key operational flow is documented with explicit owner/session trust split.
3. Evidence artifacts are produced (request id, policy decision, tx hash linkage).
4. README/runbook includes setup, env vars, and known failure modes.
5. CI checks for example smoke path and docs links pass.

Deliverables

• Adapter package/module + example
• Integration runbook
• Security/trust-boundary section
• Test/smoke script for basic flow

Definition of done

• Acceptance criteria complete
• Maintainer sign-off from runtime + security perspective
• Linked back to Lucid Agents + starknet-agentic integration status? #265 for user-facing status closure