feat(gen-owl): emit IRI-valued metadata as IRIs

[jdsika]

Summary

Fixes # — implements the proposal of linkml#3546 ("gen-owl emits rdfs:isDefinedBy and dcterms:license as string literals instead of URIs") and extends it to the ontology header.

gen-owl renders every annotations entry and every string-ranged metadata slot as a literal. For properties whose value is a resource by their own specification that is wrong: an ontology's owl:priorVersion, owl:versionIRI, prov:wasDerivedFrom, dcterms:license or dcterms:conformsTo comes out as "https://...", which tools reading the header can neither dereference nor follow. Before this change there was no way to express these header terms as IRIs at all.

A value of one of the properties below is now emitted as an IRI when it is an absolute IRI or a CURIE with a declared prefix. Every other value, and every other property, keeps its literal.

Properties	Why their value is a resource
owl:versionIRI, owl:priorVersion, owl:backwardCompatibleWith, owl:incompatibleWith	OWL 2 Structural Specification §3.1, §3.5
rdfs:seeAlso, rdfs:isDefinedBy	rdfs:range rdfs:Resource (RDF Schema 1.1 §5.4)
dcterms:license, conformsTo, relation, references, isReferencedBy, hasVersion, isVersionOf, replaces, isReplacedBy, requires, isRequiredBy, source	DCMI Metadata Terms relating a resource to another resource
prov:wasDerivedFrom, prov:wasRevisionOf, prov:hadPrimarySource	rdfs:range prov:Entity (PROV-O)

id: https://example.org/onto/v2
license: https://www.eclipse.org/legal/epl-2.0/
annotations:
  owl:versionInfo: v2
  owl:priorVersion: ex:onto/v1
  prov:wasDerivedFrom: https://example.org/releases/tag/v2.0.0

<https://example.org/onto/v2> a owl:Ontology ;
    owl:versionInfo "v2" ;
    owl:priorVersion <https://example.org/onto/v1> ;
    prov:wasDerivedFrom <https://example.org/releases/tag/v2.0.0> ;
    dcterms:license <https://www.eclipse.org/legal/epl-2.0/> .

• Applies to the schema header, classes, slots and permissible values alike: one helper, called from the metaslot loop (the string-ranged license and conforms_to) and from the annotation loop.
• dcterms:identifier is not listed: DCMI gives it the range rdfs:Literal.

How was this tested?

• New test_iri_valued_metadata_is_emitted_as_iris: absolute IRI, expanded CURIE, PROV, DCMI as annotations, and license / conforms_to / see_also as metamodel slots.
• New test_literal_valued_metadata_stays_literal: owl:versionInfo, dcterms:identifier with an IRI-looking value, dcterms:creator, and an IRI-valued property with plain text all keep their literals.
• pytest tests/linkml/test_generators -m "not kroki" — 1774 passed, 41 skipped, 3 xfailed.
• Slow-test snapshots regenerated with --with-slow --with-biolink --generate-snapshots. The diff is the intended change only, three lines: meta.owl gets dcterms:license <https://creativecommons.org/publicdomain/zero/1.0/> and dcterms:conformsTo <https://www.rfc-editor.org/rfc/bcp/bcp47.txt>, biolink.owl.ttl gets dct:license <https://creativecommons.org/publicdomain/zero/1.0/>, each previously a string literal.
• ruff check and ruff format --check (0.11.13) clean.

Areas of uncertainty

• The property list is curated. It is limited to properties whose specification ranges them over resources. A property outside it keeps literals even when its value is an IRI, as before.
• A CURIE with an undeclared prefix is a syntactically valid absolute IRI (its prefix reads as a scheme) and is emitted as such. Declaring the prefix gives the expanded form.

Checklist

• My code follows the contributor guidelines
• I have added tests that prove my fix/feature works
• Existing tests pass locally with my changes

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