🧪 [test] Add test coverage for WeightGate.set_weight

[dioncx]

🎯 What: Added tests for the previously untested set_weight method in WeightGate.
📊 Coverage: The new test_set_weight method covers:

• Setting the weight of an existing association
• Setting the weight of a new association
• Clamping of weights to the [0.0, 1.0] bounds
• Implicit saving by verifying persistence when loading into a new instance
  ✨ Result: Increased test coverage and ensured reliability of the state mutation in WeightGate.

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PR created automatically by Jules for task 18235223713620428121 started by @dioncx

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