Integration + provider layer types + RuntimeServices threading

[aram356]

Description

Migrate integration layer (IntegrationProxy::handle, handle_proxy) and auction provider layer (AuctionProvider::request_bids → async, AuctionContext gets RuntimeServices) to platform-agnostic types. Thread RuntimeServices through all integration and provider call sites. Migrate send/send_async calls deferred from PR 6.

Done when

• All 6 sub-slice checks pass (IntegrationProxy, handle_proxy, AuctionContext, AuctionProvider, orchestrator callers, entry point callers)
• request_bids is async
• Per-PR gates pass

Blocked by

PR 12

References

• docs/internal/EDGEZERO_MIGRATION.md — Phase 2, PR 13
• Part of EdgeZero migration #480