6a98e8cd9c
- 14 tolerance types: flatness, parallelism, perpendicularity, concentricity, position, etc. - GDTFeature control frame with symbols, modifiers (MMC/LMC/P), datum refs - Validation: flatness/parallelism/perpendicularity/concentricity/position - DXF export for GD&T annotations - 22 tests: all symbols, modifiers, validation, DXF export