feat: update models vrs 2.1.1-ballot.2026-09.1

[korikuzma]

Changes

• update models vrs 2.1.1-ballot.2026-09.1 and gkm-core 1.3.0-ballot.2026-09.1
  • Added _abstract classvar
  • GKS -> GKM (deprecating classes that start with GKS)
  • Adds missing RelativeAllele to Variation root

Schema changes

note: Use /json rather than *-source.yaml

• Core changes: https://github.com/ga4gh/gkm-core/compare/1.2.0..1.3.0-ballot.2026-09.1
• VRS changes: https://github.com/ga4gh/vrs/compare/2.1.0..2.1.1-ballot.2026-09.1

[larrybabb]

Here's a claude review

Findings

1. (Medium) packaging is imported but not a declared dependency. metadata.py:6 adds from packaging.version import Version at module top level, but packaging isn't in pyproject.toml's runtime dependencies (pydantic, bioutils, requests, canonicaljson, typing-extensions). I confirmed in the venv that packaging is Required-by only dev/notebook tools (pytest, sphinx, jupyter) — none of the runtime deps pull it. A minimal pip install ga4gh.vrs[extras] could therefore fail at import ga4gh.core.metadata with ModuleNotFoundError. In practice packaging is near-ubiquitous, so it likely won't bite most users and CI never sees it — but for a reference library an undeclared top-level import is a real gap.

   • Fix: add "packaging" to dependencies, or avoid the dep entirely by comparing pydantic.VERSION (a tuple-parseable string pydantic already exposes).

[larrybabb]

+1