feat(export): name the standard library elements a converted model references (#731)

[someshSandbox]

Fixes #731.

package L {
    private import ScalarValues::Real;
    private import ISQ::*;
    part def Car {
        attribute speed : Real;
        attribute weight : MassValue;
        attribute count : ScalarValues::Integer;
    }
}

sysml l.sysml -convert api-json:

	develop	this PR
@ids referenced but not in the output	5 normative ids, e.g. 14c0aa22-5489-59b5-b438-ded26e83ba31	none
ScalarValues::Real	only its id	{"@type": "DataType", "@id": "14c0aa22-…", "elementId": "14c0aa22-…", "qualifiedName": "ScalarValues::Real", "declaredName": "Real", "isLibraryElement": true}
ISQ (imported namespace)	only its id	a LibraryPackage with the same properties
import ScalarValues::Real (importedMembership)	only its id	an OwningMembership with memberElement → Real, isLibraryElement: true

A referenced library element is stated under its normative id, and nothing more is written about it:

• It carries its metaclass, elementId, qualifiedName and declaredName, and isLibraryElement: true (KerML Element::isLibraryElement, Element_isLibraryElement in the ontology).
• Its owner, members and relationships stay in the library, and the library isn't exported.

Change:

• Writer: claimLibrary records each library element a document links to. libraryNames then states the ones the output references, after the normative relationships are materialized. A library package is a LibraryPackage. An alias, or an element with no metaclass to state, isn't stated, and neither is its membership.
• The API JSON root namespace takes only the document's own unowned elements, not the stated library elements (LibraryReference).
• Reader: such an element is a reference into the bundled library, not a declaration, and isn't written back. It is refused when its qualified name isn't the one the library gives its id, or when the library has no such id. A library membership must own such an element.
• Repository sync ignores them: a library element is never created, changed or deleted in a repository.
• rdf-mapping.md describes them.

Tests:

• tests/export/library_names_test.go:
  • every @id the output references is an element of it;
  • the metaclasses stated for Real, Integer, MassValue and ISQ;
  • no owner on a stated library element;
  • one membership for the membership import;
  • a graph-only round trip and an API JSON round trip give the same notation back;
  • a library element named otherwise than the library names it is refused.
• 13 .golden.ttl files are regenerated. The diff only adds the stated library elements (29), no line removed.
• TestFixtureElementIDsRoundTrip skips stated library elements, which keep the normative id the references to them carry. TestToolkitReExportTable counts model elements only.
• internal/translate/..., tests/export/..., tests/corpus/..., tests/identity/..., tests/reposync/..., tests/grpc/..., internal/frontend/grpc/..., internal/workspace/... and internal/check/... pass.
• The example is valid for sysml -validate.

🤖 Generated with Claude Code

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[HuiJun]

Accepted! Thank you!