[kvlonge]

Why

A SQL test fixture can supply a contracted column as bare NULL, leaving the warehouse with an untyped boundary even though SQLBuild already knows the authoritative relation type. Type-sensitive downstream expressions can then fail compilation for otherwise valid empty fixtures.

Changes

• retain direct bare-NULL projection facts during fixture inference;
• cast only those null-only outputs to authoritative expected types during fixture completion;
• preserve explicit types, set-operation values, unknown expressions, and quoted/unquoted identifier semantics across adapters;
• keep fixture inference to one pass per fixture;
• add unit, integration, and CLI E2E regression coverage.

Verification

• 49 focused fixture inference, completion, and SQL-test assembly tests;
• 14 focused post-review adapter and edge-case tests;
• make check-ci;
• sanctioned unit and integration suite: 6,776 passed;
• independent read-only review with both findings fixed;
• public-repository hygiene scan and publication hooks.