No literal 26 exists anywhere, so the GamePart id is computed. That does not stop
it being found: the id is KNOWN at each screen from the GamePart table (EXTRAS = 5,
MISSION SELECT = 7), so snapshot both and intersect. New tool diff_words.py does
the classic differential search over the sparse guest image, and find_partslot.sh
drives the two screens and runs it.
Result: 171 MB scanned, exactly 4 addresses read 5 then 7 -- 0x708FFBEC,
0x708FFCBC, 0x708FFDAC, 0x708FFE20 -- and all four are guest STACK (the same run's
log puts thread stacks at 0x709...). So the requested part id exists only as a
stack argument in flight; there is no persistent field, which is consistent with
finding no literal store, and means there is nothing stable to poke.
That closes the last memory-and-menu route to the challenge missions. Reaching
them needs either the genuine in-game unlock (an in-mission attainment, per
AVSCRIPT_COMMAND_ATTAINMENT_CHALLENGE_MISSION_CARGO_SCORE) or an emulator-side
hook that forces the transition -- a code change, not a poke.
diff_words.py is worth keeping well beyond this question: it locates any field
whose address is unknown but whose value is known at two moments.
