Add Isometric 3D mode with Guide Lines

While doing Isometric drawing, be able to have some guide lines or constrainted tools to keep the line in main directions.

Need to be able to define the type of isometric angle.

No files, tests, or entry points are named. Start by reviewing the existing drawing workflow and how isometric angles are represented; clarify the supported angle choices, guide-line directions, and constrained-tool behavior. Done means the requested isometric mode and angle selection are defined and verifiable in the pixel editor.

Written by the indexing model from the issue text.