chore: Specify API host for runtime, deriving other addresses as needed

[jsantell]

Currently, when the runtime connects to an incorrect/invalid server (e.g. forgetting to run local server), the web socket connection retries until success, leaving the runtime initialization hanging. A general "API host" URL is needed for the runtime in order to ping the status, which would circumvent this socket loop scenario and alert that the
server is invalid. A simple health ping check has been added.

With an API host URL, other runtime values can be derived, removing redundant params.

With static asset cache no longer explicit, and all but runtime usage of StaticCache being in a Deno environment, the StaticCache functionality now explicitly uses HTTP or the filesystem (StaticCacheHTTP and
StaticCacheFS).

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Summary by cubic

Switch Runtime to a single apiUrl host and derive storage and static addresses internally. Shell now performs a runtime health check to catch wrong-backend connections early.

• Refactors

  • RuntimeOptions now requires apiUrl; removed blobbyServerUrl and staticAssetServerUrl.
  • Static assets default to "/static" on apiUrl; storage paths are built from apiUrl (e.g., "/api/storage/memory").
  • Added Runtime.healthCheck(); toolshed exposes "/_health" with CORS.
  • Updated services, CLI, shell, tests, and README to use apiUrl.

• Migration

  • Replace blobbyServerUrl with apiUrl in all Runtime instantiations.
  • Remove staticAssetServerUrl; ensure static assets are served from "/static" on the API host.
  • Make "/_health" accessible from the shell (CORS/proxy as needed).