[kvlonge]

Why

SQL tests currently repeat explicit typed-null projections even when relation metadata already provides authoritative column types. Zero-row fixtures also require authors to restate every column solely to preserve schema shape.

Changes

• infer bare NULL AS column types for expected outputs as well as mocked relations
• add SELECT * FROM __empty_fixture() for schema-known zero-row input and expected fixtures
• let sqb format remove redundant typed-null mock columns when planner completion proves the rewrite safe
• preserve authored SQL for set operations, macro-expanded fixtures, disabled SQL analysis, and ambiguous source mappings

Verification

• focused compiler, planner, lint, integration, and DuckDB E2E tests: 102 passed
• make check-ci
• public repository hygiene scan

Tracking: CHI-321