test: cover a complete generated-schema document end to end

[jdsika]

Adds the document-level correctness net that #61's canary implies: a complete,
naturalistic generated-schema document, checked end to end.

Why

From the linkml/linkml#3985 review, this comment:

i think that there should be a graph isomorphism test with a complex
naturalistic schema, but that might work better in the downstream package
tests than here - another test i was looking for and did not find was "is the
transformation here correct across the fuckery that is possible in RDF"

The seeded graphs in properties/ exercise each hard shape on its own. This
covers the other risk: one document where they interact.

What

tests/integration/test_naturalistic_schema.py - an OWL/SHACL document that
combines, in a single graph:

• two owl:unionOf lists sharing a tail cell, and a list whose member is a list
• a blank node referenced from two subjects, and a blank-node cycle
• OWL restrictions, SHACL property shapes, and an sh:ignoredProperties list
• language-tagged, plain, empty, escaped, unicode and typed literals, and rdf:nil

Eight tests, 32 cases: isomorphic round-trip, idempotence, blank-node-label
independence and insertion-order independence across all seven public
renderings, plus diff locality on a realistic edit. A guard test asserts the
fixture still contains each hard shape, so the rest cannot pass vacuously.

The behavior it pins down

Adding one unrelated class to that document:

RDFC-1.0 only :  40 existing lines rewritten by the edit
diff-stable   :   0 existing lines rewritten by the edit

test_adding_a_class_rewrites_nothing_rdfc_alone_would_rewrite asserts both
arms, so a fixture that stopped demonstrating the problem fails instead of
passing quietly.

Requirement catalog

RDF-ISOMORPHISM and TURTLE-STABILITY described only seeded graphs, and both
they and WL-COMPONENTS declared their end-to-end dimension not-applicable.
The new cases are mapped as end-to-end evidence on all three, the descriptions
updated, and coverage.md regenerated.

No release

No src/ change, so no behavior or emitted-byte change, and no changelog entry

• matching test: connect standards requirements to collected coverage #57, the comparable tests-only change.

Local verification: 1259 passed, coverage 96.13% (gate 95%),
check_requirements.py and check_standards.py clean, ruff check and format clean.