SDKs 0.20.1: release metadata resolution

All four SDKs now expose read-only release metadata resolution through POST /releases/resolve: ordered single-video identities, Site/Actor context, candidate alternatives, explicit per-entry decisions, nullable dates, opaque versions and recheck times. Packs remain unsupported. Existing file-identification and feed contracts are unchanged.

The new route carries typed validation, authentication, quota, body/media and service problems. Shared contract tests cover all four adapters; C# consumer coverage includes preferences, ownership, unchanged rechecks and Retry-After. Go now sends plain JSON rather than Kiota's default gzip request bodies, matching the API and other SDKs.

Python prdb-sdk, TypeScript @prdb/sdk, Go module github.com/prdb-net/prdb-sdk/go (tag go/v0.20.1) and C# Prdb.Sdk share version 0.20.1. Prdb.Hashing is unchanged. See the release-resolution guide and changelog for safe automatic selection and the distinction from independent file/hash confirmation.

The patch also restores TypeScript API-key binding with both older locked and newer freshly resolved Kiota dependencies for supported base URLs with explicit ports. CI verifies both dependency resolutions; origin validation and cross-origin redirect protection remain enforced.

The API consumer acceptance passed against both Prdb.Sdk 0.20.0 and 0.20.1 downloaded from NuGet. Published Python, TypeScript and Go 0.20.1 packages also passed real HTTP resolution with the synthetic API fixture. No SDK checkout substitutes for the released-package acceptance.