docs(changelog): record person-fit Monte Carlo execution repair

Author: seonghobae

docs/changelog.d/1779-personfit-mc-execution.md

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+# Execute deterministic person-fit Monte Carlo acceptance
+
+## Fixed
+
+Run the existing 500-replication person-fit U3 reversed-respondent acceptance in the normal Rust test suite instead of leaving it behind `#[ignore]`. The simulation design, respondent/item counts, fixed-seed reproducibility, public `person_fit_np` call, and >=95% detection criterion are unchanged.