Fix SpeciatedFitnessEliminator to sort FitnessObserver inputs by raw fitness

[Copilot]

• Update SpeciatedFitnessEliminator::eliminate (non-rayon + rayon) to sort observer inputs by raw fitness before calling observer
• Add doc comment to FitnessObserver::observe noting inputs are sorted descending by fitness
• Add test observer_receives_fitness_sorted_by_raw_descending verifying observer receives raw-fitness-descending order
• Fix test: construct genomes with the low-fitness genome first so the input is deliberately unsorted, making the test fail if sorting is absent

Original prompt

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This section details on the original issue you should resolve

<issue_title>New FitnessObserver fix still doesn't quite sort exactly as previously</issue_title>
<issue_description>The new FitnessObserver fix does use the correct fitness, but it is still sorted by the species-balanced versions. However, I think it should be implied that FitnessObserver inputs should always be sorted by fitness. Might incur extra performance cost though.

Probably should also add a doc comment about it being sorted before passed in.</issue_description>

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

• Fixes New FitnessObserver fix still doesn't quite sort exactly as previously #154

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[Copilot]

Pull request overview

This PR fixes SpeciatedFitnessEliminator so FitnessObserver::observe receives fitness values sorted by raw (pre-division) fitness, aligning the ordering with the values being observed while preserving speciation-aware elimination behavior (which still uses divided fitness).

Changes:

• Sort observer inputs by raw fitness (rayon + non-rayon), then re-sort by divided fitness for truncation/selection.
• Document FitnessObserver::observe input ordering contract (descending by fitness).
• Add an integration test validating raw-fitness ordering for observer inputs under speciation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
genetic-rs-common/src/builtin/eliminator.rs	Adjusts SpeciatedFitnessEliminator::eliminate to sort observer inputs by raw fitness and adds a doc note about descending order.
genetic-rs/tests/speciation.rs	Adds a new test ensuring the speciated eliminator’s observer sees raw fitness values in descending order.

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