bug: make shape snapping less aggressive for crayon and coloring strokes

[markm39]

Problem

Shape snapping can be too aggressive for coloring or crayon-like strokes. When the user is filling/coloring an area, the gesture can be incorrectly recognized as a shape and converted away from the intended freehand stroke.

Expected behavior

Shape recognition should not interfere with coloring tools or broad crayon/highlighter-style gestures. Users should be able to color freely without accidental shape conversion.

Possible fixes

• Disable shape recognition for crayon/coloring tools.
• Use stricter shape-recognition thresholds for broad/textured tools.
• Require a cleaner geometry signal before snapping non-pen strokes.
• Make shape snapping tool-configurable.

Acceptance criteria

• Crayon/coloring strokes do not accidentally snap to shapes.
• Pen shape recognition still works for intentional shapes.
• Shape recognition behavior is covered by focused tests where practical.