re: the screen parse generalises to the ARSENAL, plus kind 0x4 and the component model

examples/screen_layout.rs dumps a bundle's declaration table and placement region
together. It reproduces the tutorial pause menu exactly and reads the ARSENAL the
same way -- 23 elements that match the running game: eight buttons prbtn1..8.rat
at X=242 evenly spaced (the config declares WEAPON_CATEGORIES = 8, and eight
categories are what the Arsenal shows), prexp3.t32 declared SEVEN times at X=726
34px apart (the DATA SHEET rows), prexp1 sliding (726,143)->(1286,143) with
prexp1a parented to it, and prmsg at (151,645).

Two additions to the format:

  kind = 0x4 marks a REPEATED INSTANCE of a sprite -- prexp3.t32 appears once
  with 0x0 then six times with 0x4, each with its own placement. So the element
  name is not a key; the declaration index is.

  A screen composes from named .prt components. GP_HANGAR_ARSENAL.pak has 510
  RATC entries because its config names components (Menu = prmain_scr.prt, etc.)
  and they resolve under the config's own PATH prefix: prmain_scr.prt is absent,
  eng\prmain_scr.prt is present -- the same <lang>+<member> convention the movie
  table uses. A sub-component reads identically: psselect_win1 declares 4
  elements, three parented to element 0.

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

docs/re/structures/ui-rat-layout.md

@@ -227,3 +227,37 @@ recording them because a static-only reading would have shipped them:
   [weapon-datasheet-runtime.md](../weapon-datasheet-runtime.md) is a ready-made oracle for it.
 - Tooling: `crates/sylpheed-formats/examples/ui_screen.rs` (inventory a screen pak, carve a
   named RATC child), `sylpheed-cli pak textures` (decode every sprite).
+
+## It generalises: the ARSENAL screen, and how a multi-component screen composes
+
+**2026-08-11.** [`examples/screen_layout.rs`](../../../crates/sylpheed-formats/examples/screen_layout.rs)
+dumps a bundle's declaration table and placement region together. It reproduces
+the tutorial pause menu exactly, and it reads the ARSENAL the same way
+([capture](../captures/arsenal-main-screen-layout.txt)) — 23 elements that match
+the running game:
+
+- **Eight buttons** `prbtn1…8.rat` at **X=242**, Y `166, 220, 276, 331, 385, 441,
+  496, 551` — evenly spaced, and eight is exactly what the screen's own config
+  declares with `WEAPON_CATEGORIES = 8` (GUN, BEAM, LASER, MPM, ASM, B/R, CANNON,
+  SPECIAL, the list photographed in the Arsenal).
+- **`prexp3.t32` declared seven times** at X=726, 34 px apart (`381 … 585`) — the
+  DATA SHEET's rows.
+- `prexp1.t32` animates `(726,143) → (1286,143)`, sliding off the right edge, with
+  `prexp1a.t32` **parented to it** (`parent = 13`).
+- `prmsg.t32` at (151,645) — the description line along the bottom.
+
+### Two things this adds
+
+- **`kind = 0x4` marks a repeated instance.** `prexp3.t32` appears once with
+  `kind 0x0` and then six more times with `0x4`, each with its own placement — the
+  game repeats one row template rather than shipping seven sprites. So the element
+  *name* is not a key; the declaration index is.
+- **A screen is composed of named components.** The pause menu is one bundle, but
+  `GP_HANGAR_ARSENAL.pak` holds **510** RATC entries because its screens are built
+  from the `.prt` components its config names (`Menu = prmain_scr.prt`,
+  `Select_Window = prselect_scr.prt`, `Detail_Window_Known = prselect_win3.prt`, …).
+  Those resolve **under the config's own `PATH` prefix**: `prmain_scr.prt` is not
+  present, `eng\prmain_scr.prt` is — the same `<lang>+<member>` convention the
+  [movie table](../movie-subtitle-link.md) uses. A sub-component reads identically:
+  `psselect_win1` declares 4 elements, three of them **parented to element 0**,
+  which is the parent-index field doing real work on an independent pak.