- Add warn() for non-fatal parse errors (like Zig's Parse.warn)
- Implement finishAssignDestructureExpr for destructuring assignments
- Use parseBlockExpr instead of parseBlock in for/while statement bodies
- Use parseSingleAssignExpr in switch prongs
- Enable x86_64/CodeGen.zig corpus entry
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>