re: what the game actually reads at boot -- config.ini, and which

GameParts exist at all

Q6's second half, advanced but not closed, and the negative is the point.

config.ini is the disc's ONLY config file -- one find over the whole
extract -- and its own Shift-JIS header calls it the "Application /
GamePart initial settings table". Its [SYSTEM] section, which that same
comment says holds what the game and every game part share, is EMPTY. So
the boot order is not in disc-side configuration at all, and that search
space is now closed rather than merely unexplored.

What the file DOES carry is the language: XC_LANGUAGE_* -> eng/jpn/deu/
fra/esp/ita, defaulting to eng. That is the mechanism behind the EN/JP
build pairs in GP_TITLE and the <lang>.pak families -- a question the
corpus had described but never traced to its input.

Then the registry. Pulling every RegisterToFactory diagnostic string
binds 24 of the 29 GamePart ids to a C++ class, and five ids have no
registration site: 1, 2, 16, 18, 28. Id 1 is GP_ADVERTISE_DEMO, which
agrees with what I measured two iterations ago -- the attract loop is the
TITLE replaying ADV.wmv, not a transition into an advertise part. Marked
amber, not green: it is an argument from an error message, not from code.

Two things fall out for Q4: ids 3 and 4 are the same class
(GamePart_SaveLoad, one part with two ids), and the menu buttons' ids now
match the executable's own class names rather than a list of table names.
Still a name match, one level closer to the code.

What is still missing is the transitions themselves, and I say so: the
manifest gives the boot-side assets, config.ini the language, the
registry which parts exist. What decides to advance is in
GamePart_Title's code and that dig has not been started.

docs/re/INDEX.md

@@ -153,6 +153,7 @@ files, which is how the same ground got covered twice.
 | [`menu-navigation-semantics.md`](menu-navigation-semantics.md) | The title menu — how it moves, and where each button goes |  ✅ measured: wraps both ends, Ⓑ restores focus, ⬅➡ inert; 4 of 5 destinations driven. 🟡 GamePart id is a name match, ❔ `NEW GAME` untested |
 | [`screen-transitions.md`](screen-transitions.md) | Between two screens — a fade through black, and where its timing lives |  ✅ the fade quad's keyframe group is decoded (disc-wide: per-pak all-or-nothing; `GP_TITLE` = the 6 screens, not the 6 overlays); the ~0.4 s fade-OUT is measured, not on the disc |
 | [`menu-audio-cues.md`](menu-audio-cues.md) | Menu audio — the event vocabulary is on the disc, the binding is not |  ✅ `SE_UI_*` cue names/ids decoded and `BANK_SE`→`Static.slb` (0/322 in FILES); 🟡 event binding is a name match; ❔ `Static.slb` has no wave boundaries, so SE audio is not extractable |
+| [`boot-config-and-gamepart-registry.md`](boot-config-and-gamepart-registry.md) | What the game reads at boot — `config.ini`, and which GameParts exist |  ✅ `config.ini` selects the language (the disc's only config); ❔ its `[SYSTEM]` is empty so the boot order is not in config; 🟡 24/29 ids bind to a class, `GP_ADVERTISE_DEMO` is never registered |
 | [`movie-binding.md`](movie-binding.md) | Which movie plays where — boot intro, attract loop, new-game intro |  ✅ decoded from the movie manifest (`ADVERTISE_MOVIE`→`ADV.wmv`, `MS00A`→`S00A.wmv`); attract identity confirmed independently by frame matching; 🟡 skippability unsettled |
 | [`ready-room-probe.md`](ready-room-probe.md) | S1 — the Ready Room probe: no-go, and not for the reason expected |  ✅ it is 2D and enumerates (60 builds), but the pak is briefing/tactical-map content; and `kind == 0x3002` finds 0 buttons there |
 | [`ui-title-build-map.md`](ui-title-build-map.md) | Which `GP_TITLE` build is which screen state |  ✅ CONFIRMED for title / `PRESS Ⓐ` / main menu / `EXTRAS` against live captures; the archive is 8 screens × EN/JP, and "6/8/9 are submenus" is withdrawn |