docs: pin standards references and define conformance scope

[jdsika]

Summary

• Pin 14 complete original standards and seven license/provenance assets with
  exact source URLs, publication identities, checksums and byte-preserving Git attributes.
• Define the supported standards profile and distinguish normative requirements,
  informative explanations, dependency canonicalization and project ordering rules.
• Add an offline reference validator and 82 generic metadata, corruption, path,
  URL and command-line contract tests.
• Correct RDF graph-comparison and JSON-LD ordering citations and include the
  reference collection in source distributions without adding wheel runtime assets.

Verification

• Independent review approved the exact tree after malformed-input counterchecks.
• Source suite: 1,025 tests pass, 95.55% runtime coverage.
• Standards/documentation: 112 tests pass at minimum and newest dependency versions.
• Ruff, mypy, distribution metadata and source-archive content checks pass.
• All eight runtime module ASTs are unchanged after removing docstrings; all
  eight runnable examples and six API signature blocks are unchanged.
• Original asset hashes survive a checkout with core.autocrlf=true.
• Final exact-wheel suite: 1,023 tests pass with two expected source-only skips,
  despite hostile inherited source-path and pytest settings; package origin and
  unchanged artifact digest verified in a clean environment.
• The platform/Python CI matrix must pass before merge.

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