fix(evm): correct favored threshold comparison

[MozirDmitriy]

Motivation

The selection criterion is inverted:

• Comment: “selected” if the proportion of new finds is above the threshold.
• Code: is_favored is set when the proportion is below the threshold (< FAVORABILITY_THRESHOLD).
• This reverses the meaning and distorts metrics.favored_items.

Solution

• Fix incorrect favored comparison from < to > so only productive corpus entries (ratio > threshold) are marked as favored.
• Add unit tests to assert favored transitions (> threshold true, < threshold false, == threshold false with strict >) and eviction behavior (favored protected, non‑favored evicted).
• This prevents productive seeds from being evicted and aligns code with documented intent.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[grandizzy]

thank you! oh, I think you're on to something here, indeed if for example 40 new finds produced from 100 mutations that would be 0.4 while if only let's say 20 new finds from 100 mutations that will make 0.2 so indeed favored should be determined by greater than 0.3
Will make some tests with this fix, meanwhile mind to fix the failing favored_sets_false_and_metrics_decrement_when_ratio_lt_threshold test you added?
CC @0xalpharush

[0xalpharush]

This seems right. The refactoring I made here should have inverted it like is done in this PR. Thanks @MozirDmitriy
https://github.com/foundry-rs/foundry/pull/10988/files#diff-6672478b3ff4d87907eb18ba56f9037395efbe25bb567b668d9b82a580d0b0c5L298-L299

[grandizzy]

lgtm, thank you!