[kvlonge]

Why

A direct projected column filtered by IS NOT NULL remained nullable in inferred output facts. This produced a false contract diagnostic even though the SQL filter proves the output is non-null.

Changes

• infer direct projected columns as non-null when a conjunctive IS NOT NULL filter proves that fact
• preserve scope across aliases, self-joins, outer joins, and CTE boundaries
• apply the same refinement to compact and AST analysis paths

Verification

• uv run pytest tests/unit/src/sqlbuild/compiler/compile/_helpers/test_sql_analysis_columns.py -n auto --dist loadfile
• uv run fensu check
• uv sync --all-extras
• make check-ci
• public-repository hygiene scan
• cache-free static compile of the downstream 974-model project: 0 errors, 0 warnings