Fix StrategyResult.resolve() mutating internal weights

[dotsdl]

Summary

• resolve() referenced self._weights directly, so each call normalized the dict in-place. A second call would double-normalize, producing wrong results.
• Fix: copy the dict before modifying it.
• Added tests for non-mutation and idempotency.

Test plan

• test_resolve_does_not_mutate_weights — verifies weights unchanged after resolve()
• test_resolve_is_idempotent — verifies two consecutive resolve() calls return the same result

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[ianmkenney]

resolve() referenced self._weights directly, so each call normalized the dict in-place. A second call would double-normalize, producing wrong results.

To clarify, resolve mutates _weights, but repeated calls do not produce wrong results since normalizing normalized weights doesn't do anything.

Regardless closing in favor of #19