cbf52ba9f9
Closes the 4-byte record key. tag_hash is name_hash's shape -- byte-sum checksum in the top byte over a 24-bit modular polynomial -- with two different constants: modulus 0x00FFFFDF (2^24-33, prime) instead of 0x00FFF9D7, and no lowercasing, so tags are case-sensitive. name_hash explains 0 of 8643. Recovered from the tables rather than the executable: every inline field name is a known (name -> tag) pair, and comparing names differing in one character gives the per-position weights 1, 0x100, 0x10000, 0x21, 0x2100, ... -- a byte leaving bit 24 re-enters as 33, i.e. reduction mod 2^24-33. Holds where it is easy to get wrong (distance 8 and 9 carry correctly). A record's key is the tag of its own name: FormationSet rosters 362/362, UnitGroup rosters 281/281, S02 squadron names 111/111 -- so records can be addressed by name without reading the roster first. Implemented in Python (unitgroup.tag_hash) and Rust (sylpheed_formats::hash::tag_hash) with 3 new unit tests carrying disc-derived vectors; cargo test -p sylpheed-formats --lib hash is 8/8 green. Not settled: the guest routine is unlocated, so this uses exact modular arithmetic where the game may use a Barrett step without final fixup.