fix(gfql): validate absent relationship types - #2003

Summary

• Make strict validation reject a typed relationship when the edge schema proves the type absent.
• Preserve the generic type-carrier case as unjudgeable without scanning instance values.
• Treat an explicitly declared empty relationship-type catalog as judgeable and empty.
• Record the fix under [Development] in CHANGELOG.md.

This closes the validator/executor agreement residual tracked by #1916 without changing default strictness, the declared-schema API, or remote behavior.

Final linear state

• Head: 76d87ab22639075394d5536de8e2e2f175a48e37
• Base: master at merged fix(gfql): preserve boolean sum zero on polars gpu #2002 commit fcf369fb920a280030706ce672fdd1a28a4440e6
• Topology: four linear, one-parent commits; zero merge commits
• Incremental diff: four files, +48/-7

The three reviewed implementation/test patches are range-diff exact after the final rebase. The fourth commit adds only the requested changelog entry.

Relationship-type judgement boundary

The strict binder has four pinned states:

• No relationship-type carrier and no declarations: the schema proves the requested type absent, so strict validation raises typed E301.
• Generic type carrier without declarations: membership is unjudgeable without scanning values, so validation defers.
• Generic carrier with an explicitly empty declared catalog: the declaration proves no type exists, so strict validation raises.
• Nonempty declared catalog: strict validation judges ordinary membership.

Validation

• Focused CPU boundary selection: 6 passed, 232 deselected.
• Master-relative diff-check and added-line prohibited-token/broad-str scan: clean.
• Canonical type-hygiene guard: no growth.
• ./bin/lint.sh: clean, including Ruff, comment-density, and import guards.
• ./bin/typecheck.sh: mypy 2.3.1, 336 source files, zero issues.
• No Docker, local GPU, DGX, or broad local suite was used.

Review resolution

• Boundary sufficiency question: resolved by the direct explicit-empty-catalog case, alongside the no-carrier and generic-carrier controls.
• The branch is directly linear on merged fix(gfql): preserve boolean sum zero on polars gpu #2002 with no predecessor diff leakage.

Landing

Review the master-relative range fcf369fb9...76d87ab22.

After this exact-head CI generation is green, the authorized landing method is GitHub Create a merge commit with admin override. Retain the source branch.