Cover auction path against real platform config stores (Viceroy config-store, Cloudflare KV) via manifest binding name

[aram356]

Summary

PR #110 added config-seeded auction coverage through the Fastly and Cloudflare adapters, but it seeds the config store in-process rather than through each platform's real store. This closes the last mile: prove the auction path works against the actual platform config store, opened by its manifest binding name.

What PR #110 already covers

crates/mocktioneer-adapter-{fastly,cloudflare}/tests/contract.rs each seed a non-default bid_cpm (0.35) into an in-process ConfigStore, inject it via the service builder's with_config_handle, and dispatch POST /openrtb2/auction, asserting the decoded bid price. These run under the real wasm runtimes (Viceroy / wasm-bindgen + headless Firefox) in the existing adapter-wasm-tests CI matrix.

That exercises: request translation → config-store binding → AppConfig extractor → auction handler → response translation.

The gap

Because the handle is injected, the service builder binds it under default_key "default" (see synthesise_store_registries). So these are not covered:

• The real platform read — Fastly ConfigStore::try_open(...) / Cloudflare KV get(...).
• The manifest binding name mocktioneer_config (from [stores.config] ids), as resolved by the manifest-driven run_app path.
• Emulator/local state wiring (Viceroy config-store fixture, miniflare/workerd KV binding).

A binding-name or default-key regression in the manifest path could therefore break all edge auctions while CI stays green.

Proposed work

• Fastly: add a Viceroy config-store fixture ([local_server.config_stores]) holding the blob envelope under mocktioneer_config, and a test that dispatches an auction through the manifest-driven path.
• Cloudflare: stand up miniflare/workerd with a seeded KV binding and dispatch an auction against it.
• Spin: add the equivalent once Spin adapter cannot serve: spin-sdk 6 imports wasi:http@0.3.0-rc, unsupported by released Spin runtimes #113 (the wasi:http ABI blocker) is resolved.
• Keep the fixtures' blob envelope in sync with what config push writes (canonical JSON + SHA), ideally generated rather than hand-maintained.

Notes

• The blob is SHA-gated (BlobEnvelope), so fixtures must carry a valid sha256 — generate via mocktioneer-cli config push rather than hand-editing.
• Raised by @ChristianPavilonis in review of Adapt Mocktioneer to edgezero v0.0.4 (extensible CLI, typed config, introspection routes) #110.