Fix polygon creation: require minimum 3 points

[icoderarely]

Notes for Reviewers

• This PR fixes [Extensions] Polygon tool creates invalid shape when completed with insufficient points #169
• Polygon creation now requires at least 3 points.
• If user tries to close with fewer than 3 points, polygon creation is automatically cancelled and reset.
• Enter and Escape now follow the same close path, so validation is consistent across keyboard and UI interactions.
• Existing valid flow for 3 or more points remains unchanged.

Fix Proof:

2026-05-07.01-58-49.mp4

Signed commits

• Yes, I signed my commits.

[github-actions]

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2026-05-08 18:36 UTC

[saurabhraghuvanshii]

Thanks @icoderarely lgtm!!