Read first: ui-rat-layout.md OWNS the RATC stack and already documents
the 60-byte element declaration table and 'one bundle = one
(context x language) build of that screen'. What it does not say is how
a part is addressed when it is NOT a pak entry.
The elements of one bundle share a common name prefix, and that prefix
is the part name. GP_MAIN_GAME_E2D.pak has 130 bundles with 114
distinct element prefixes -- pgmenu_btn00, pghud_wing, pgface,
pghud_range, pgmanuva_eff0 -- exactly the in-game part names.
The 100 in-game-only .prt names match a 2D bundle prefix 68 times; the
control, the 241 shipped parts, matches ZERO. The two families are
disjoint on the test. 13 shipped parts match a bundle prefix in their
own screen pak, which is the expected shape.
Four of the five mission banners land here: pgmsg_start.prt is E2D
bundle 0x89fac252, a one-element bundle declaring pgmsg_start_sub.rat;
likewise _end_, _failed_, _restart_. pgmsg_update has no bundle at all,
consistent with having no _sub.rat.
32 in-game names still have no 2D bundle. They cluster into families
whose base name is a bundle, reading as a variant declared inside a
parent bundle -- a reading, not adopted.
Artefact +38 lines / 0 deletions; the other six regenerate
byte-identical.