[Bug] Improve automatic shape recognition logic

[maxilla-0]

Long rectangles are not recognised

Steps to reproduce

1. Trace a long rectangle
2. Hold the pen
3. Rectangle doesn't form

Samsung notes can make long rectangles btw.

Screen_Recording_20260805_202049_xnotes.mp4

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xnotes 0.8.10 (47)
samsung SM-X710
Android 16 (API 36)