Clarification needed for expansion of terms with `@container` set to `@id` and a local context with a `@base`

When expanding this compact data:

{
  "@context": {
    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns/",
    "@vocab": "https://example.org/ns#",
    "typeDescribed": {
      "@id": "rdf:type",
      "@context": {"@base": "https://example.org/ns/"},
      "@container": "@id"
    }
  },
  "@id": "/item/1",
  "typeDescribed": {
    "Item": {"label": "Item"}
  }
}

I cannot tell from the spec (step 13.8.3.7.4 of the expansion algorithm) whether the key Item will be resolved against the local context or not. Actually, reading the spec I see nothing that sets the active context to the local context of the typeDescribed before reaching 13.8.3.7.4, although I would expect that this is the intention. Both the JSON-LD Playground and the Ruby RDF Distiller do expand the above to this:

[
  {
    "@id": "/test/item/1",
    "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": [
      {
        "https://example.org/ns/label": [
          {"@value": "Item"}
        ],
        "@id": "https://example.org/ns/Item"
      }
    ]
  }
]

In the Ruby code corresponding to step 13.8.2 and onwards, IIRC, a container_context is defined and from thereon used.

Unless I've missed something in the algorithm that clarifies that something like this is required, I believe we should clarify this exhaustively in the spec, and add this test case (unless I've overlooked an existing one for this).

I've made a similar adjustment to TRLD to reflect this presumably desired behaviour.

Read step 13.8.3.7.4 of the JSON-LD expansion algorithm and compare it with lib/json/ld/expand.rb around line 615. Check the linked Ruby RDF Distiller and TRLD behavior, then clarify the specification and add a regression test for the @container: @id case with a local @base context.