Export to standard formats not implemented

[trailcode]

Description

Export of the current model to standard CAD/mesh formats (STEP, IGES, STL) is not implemented. usage.md lists "Export formats: STEP, IGES, STL" and "Export to standard formats" under File Operations, but the application does not yet provide export functionality.

Expected behavior

• File menu (or equivalent) offers an Export action.
• User can export the current document or selected shapes to at least one of: STEP, IGES, STL.
• Export uses standard formats suitable for CNC, 3D printing, or exchange with other CAD tools.

Actual behavior

• No export option is available; only save to native .ezy format exists.

Environment

• EzyCad (native and/or WebAssembly)
• OS: e.g. Windows

References

• usage.md: File Operations → Supported Formats (Export formats: STEP, IGES, STL (TODO)); Basic Operations → Import/Export.