test: connect standards requirements to collected coverage

[jdsika]

Summary

• Map 49 supported requirements and five explicit profile exclusions to their
  standard clauses or project policy, implementation owners and collected tests.
• Add an offline requirement checker that collects the suite once in an isolated
  interpreter, resolves every evidence selector against real node IDs, and
  verifies the six public callables and fifteen format aliases are all covered.
• Generate docs/standards/coverage.md from the catalog and reject a stale
  table instead of rewriting it during a check.
• Add 166 generic catalog, selector, clause, ownership and rendering contract
  tests, including mutation cases that must fail, plus a prefix-map contract test.

Verification

• Independent review approved the tree after two documented-claim corrections:
  signature blocks are described as parsed function definitions, not as checked
  against the installed API, and the collection row names the canonicalizer as a
  second responsible entry point.
• Source suite: 1,109 tests pass, 95.55% runtime coverage.
• Requirement and standards checks: 166 tests pass at both dependency endpoints,
  rdflib 6.3.2/pyoxigraph 0.5.4 and rdflib 7.6.0/pyoxigraph 0.5.11.
• Ruff, mypy, reference validator and requirement checker pass offline.
• Focused public-API selection still runs only its 11 requested tests.
• Exact-wheel suite: 1,107 tests pass with two expected source-only skips; the
  catalog, table and checker ship in the source distribution and add no wheel
  runtime assets.
• The platform/Python CI matrix must pass before merge.

No runtime behavior, dependency requirement, version or public signature changes.