re: crack the UI layout record — the retail UI rebuilds from the disc

Each UI sprite <name>.t32 ships with a <name>.rat companion, and that companion
is the layout record: big-endian u32, a 1280x720 design space at 0x18, and a
placement block of scaleX/scaleY/tint/X/Y. Animated elements repeat the block
with a trailing time field (keyframes); an 'opt ' tag carries a length-prefixed
link to the focused-state record.

Verified in that order, records first: across the four pause buttons exactly one
field varies, stepping 268/338/408/478 at a constant 70px pitch with X fixed at
226; the three items visible in a screenshot of the running game measure
346.0/415.5/485.5, mapping onto those numbers under one constant offset to
within 0.5px. The tutorial build's records are outright framebuffer coordinates,
and compositing its sprites there reproduces the screenshot pixel-accurately.

Also records two mistakes the A/B caught, since a static-only reading would have
shipped both: texture width does not identify a language (Japanese fits English
widths), and the in-mission and tutorial pause menus are separate sprite sets
rather than one set re-packed into slots.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/re/INDEX.md

@@ -22,6 +22,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | XBG7 mesh | 🟡/❔ | `sylpheed-formats/src/mesh.rs` + `tests/mesh_disc.rs` ([xbg7](structures/xbg7-mesh.md)) | weapons/props: declaration-driven variable stride (36 models), GPU-confirmed. **Stage containers: 5662 sub-models across 22 stages** via content-anchored grouped pools (`stage_models`). Quantized hero bodies (DeltaSaber `f004`) still declined |
 | Capital-ship part placement | 🟡 | `sylpheed-formats/src/ship.rs` (static) + [runtime capture](ship-placement-runtime-capture.md) | hull placement static-exact; external parts approximate statically. **Runtime capture** (Canary F10 → VS-constant WorldView) gives ground truth — validated on `e106` destroyer; not yet baked into the viewer |
 | Weapon fields defaulted on disc | ✅/🟡 | [runtime DATA SHEET](weapon-datasheet-runtime.md) | The Arsenal Gallery-Mode panel reads the live record: `Ammo Capacity` = `LoadingCount` ✅, `Max. Lock Ons` = `TriggerShotCount` ✅. Recovers `TriggerShotCount` for `wep_05`/`wep_60` (both **4**); brackets defaulted `Power`/`MaximumRange` via the letter classes. 9 of ~61 weapons reachable at 5 % save progress |
+| UI screen layout (`.rat`) | ✅/🟡 | [ui-rat-layout](structures/ui-rat-layout.md) | One pak per UI screen; each RATC = one (context × language) build; every `<name>.t32` sprite has a `<name>.rat` **layout record** (BE u32; 1280×720 design space; scale/tint/X/Y, keyframes for animated elements, `opt ` link to the focused state). **The tutorial PAUSE menu rebuilds pixel-accurately from the disc.** `loop1.rat` (screen-level draw order) not yet decoded |
 
 ## Functions / code paths