[Dalton-V]

Splitting the FRLG Box Sorter PR - 9

Helper methods for sorting the living dex

Similar to previous Box Organization helper methods. These will be used in a new Living Dex Sorter program as well as test classes.

[pa-devbot]

AI review: Reviewed against the intended usage in #1614 (PokemonFRLG_BoxSorterLivingDex + BoxSorter_Tests).

Verification

• Built the branch (CMake+Ninja like CI): compiles cleanly.
• Full command-line test suite: 20,335 passed, 0 failed.
• JSON keys natID/slug/has_gender_difference match the Pokemon HOME living dex template convention, and the "-male"/"-female" slug-suffix gender check matches PokemonHome_BoxSorterLivingDex::is_viable_for_dex. FRLG's scan_box_data does populate dex_number (National Dex via SLUGS_TO_NATIONAL_DEX), gender, and shiny, so is_viable_for_dex has the data it needs.
• make_living_dex_order logic checks out: it never drops Pokemon (template slots + extras always fit unless the overflow error fires, which is reachable: a nearly full box with shiny_dex and no shinies makes every Pokemon an extra, and the non-template slots can be fewer than the Pokemon count). Running it on already-organized boxes yields an empty plan, so it's idempotent.
• NATIONAL_DEX_SLUGS().at(nat_id - 1) in make_missing_living_dex_report is safe because the loader bounds natID to 1..386.

No blockers; two minor items below.