Move observe before truncate in FitnessEliminator

[Copilot]

Observers were only receiving the post-truncation (surviving) portion of the population, rather than the full sorted fitness list.

Changes

• genetic-rs-common/src/builtin/eliminator.rs: In both the standard and rayon eliminate implementations, call self.observer.observe(&fitnesses) before fitnesses.truncate(...).

// Before
fitnesses.truncate(median_index as usize + 1);
self.observer.observe(&fitnesses);

// After
self.observer.observe(&fitnesses);
fitnesses.truncate(median_index as usize + 1);

Original prompt

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This section details on the original issue you should resolve

<issue_title>move call to observe before truncate in FitnessEliminator</issue_title>
<issue_description>Observers shouldn't only see the upper half, but actually the full thing.</issue_description>

Comments on the Issue (you are @copilot in this section)

@HyperCodec not a super high-priority issue, but definitely something i should fix by the next update.

• Fixes move call to observe before truncate in FitnessEliminator #131

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