chore(master): release 1.6.20

[github-actions]

🤖 I have created a release beep boop

1.6.20 (2025-08-25)

Bug Fixes

• add convert from feature to structural frame (5b34346)
• add type to P1 and P2 (71ce492)
• add wrapper to convert between a feature and structural frame (676c0ef)
• allow model to set any type of feature using basefeature subclass check (97122a5)
• allow no isovalue for surfaces. Take middle as value (178d78b)
• change kwargs to build args (cb0af22)
• linting (a32ee4f)
• rename optional data argument to data for consistency (9b23bd3)
• return the first feature of a structural frame (6972062)

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[github-actions]

🤖 Created releases:

• v1.6.20

🌻