Make the plugin contract version the release version, and publish the Docker Hub overview from CI

src/plugin-host/plugin.ts

@@ -8,8 +8,10 @@ import type { RequestContext } from "../http/context.ts";
 import type { NavNode } from "../ui/nav.ts";
 import type { StorageCredentials } from "./storage.ts";
 
-// Bump major on a breaking manifest/handler change, minor on an additive one.
-export const HOST_API_VERSION = "1.0.0";
+// The Plainpages release this contract ships in — one version, not a second one to track. Its
+// major.minor must equal the release tag's; `release.yml` refuses to promote a tag that disagrees.
+// The patch digit may lag, since checkApiVersion ignores patch and auto-release cuts patches itself.
+export const HOST_API_VERSION = "0.1.0";
 
 export type HttpMethod = "DELETE" | "GET" | "HEAD" | "PATCH" | "POST" | "PUT";