re(ui): a RATC child's name is stated, not inferred -- and it was hiding every menu background

`ratc::parse` named each child by scanning backwards for the last printable run
of bytes before its magic. The format states the name explicitly instead, in an
`opt ` block: `"opt " | BE32 len | name | NUL | 3 bytes | magic` -- the same
block `ui_layout::opt_link` already read for a button's focus link.

The scan agrees with it 17 918 times out of 17 942 and is wrong 24 times, every
one the same failure: the 3 trailing payload bytes are themselves printable and
beat the real name. For `pteff05.t32` those bytes are `38 41 58` = `8AX`, so the
full-resolution background of all five menu screens registered under a name no
element declares, resolved to no sprite, and `compose` dropped it through an
early `continue` that -- unlike the two arms above it -- records nothing. The
screen lost its background and `screen render` still reported "all resolved".

`8AX` was never a name. Docs that treated it as one are corrected here.

Disc-wide, and the control is the 17 918 the scan already got right: the `opt `
reading reproduces every one of them. Effect on the five screens is the
signature of the same art at twice the resolution -- mean brightness unmoved,
high-frequency detail x1.15..x1.30 -- which is what the separately-measured
`ui-8ax-fullres-background` result said the game draws.

Also closes a long-standing dangling reference: `pmbase.t32`, recorded as "on
the disc nowhere", is the `GP_STAGE_CLEAR` child the scan called `8AX`. RATC
sibling references now resolve 10 148 of 10 148.

Verified: 114/114 sylpheed-formats unit tests (including two new ones pinning
the `8AX` case byte for byte and the no-block fallback), and every disc-gated
integration suite in sylpheed-formats/sylpheed-cli.

docs/re/INDEX.md

@@ -21,7 +21,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | IDXD nameless field keys | ✅/❌ | [idxd-unnamed-keys](structures/idxd-unnamed-keys.md) + [`tools/re-capture/idxd_unnamed_keys.py`](../../tools/re-capture/idxd_unnamed_keys.py) | Census of every field entry whose `name_off` is `0xFFFFFFFF`, disc-wide: **7 750 objects, 2 757 039 field entries, 0 parse failures**, `tag_hash` reproducing **1 271 462/1 271 462** named keys. **7 094 distinct keys are never named — and 7 052 of them are not hashes at all**, but author-assigned element ids (equal to the field's own index in 1 404 924 of 1 485 577 cases; `tag_hash("BGM_001")` is `0xC662435B` while the key valued `BGM_001.slb` is `0x000003E9`). ⚠️ **The "504 hash-keyed nameless fields" figure is 504 ENTRIES, not 504 names** — 42 distinct keys × 6 language copies × 2 records. All 42 are **ISL script-symbol hashes** in `<lang>\script\ID.tbl` (GP_READY_ROOM.pak), the link map built by `PrepareScript`'s "isl script prescanning"; 41 of 42 appear as little-endian call targets inside the `.isb` bytecode, forming a coherent launcher/helper call graph. The hash's own algebra pins the **trailing digits of 30 of the 42 names** (deltas of exactly `+0x01000001` across `stage01..09`, `stage10..16`, `challenge01..06`; `+0x01010000` across `tutorial0101..0601`). ❌ **No name was cracked, and the negative is quantified**: seven attacks up to a 3.5×10⁸ composition space found nothing above the noise floor; exhaustive preimage search recovers `"Stage01"` from its own hash but returns nothing for the real targets at ≤6 characters, and at 7 characters one target already has **1 176** preimages — a 24-bit modulus cannot name an 8+ character identifier uniquely |
 | XPR2 texture + cubemap | 🟡/✅ | `sylpheed-formats/src/texture.rs` + [colour check](xpr2-colour-check.md) | de-tile + A8R8G8B8 and DXT1. **Channel order ✅ confirmed against the running game**: the Delta Saber's decoded atlas is orange-dominant (median saturated hue 23.3°, *zero* cool pixels) and the game renders the same hull at 9.3° — a red↔blue swap would sit at ≈200°. Exact fidelity (gamma/sRGB curve, premultiplied alpha, per-channel scale) is 🟡 untested, since a hue comparison cannot see it; cubemap face ordering ❔. **2026-08-29, for the UI path only:** our composite is brighter than the emulator's frame by a gamma of **≈1.34–1.49** across three screens ([tone curve](structures/ui-render-tone-curve.md)) — 🟡 measured, not decoded, constrained only over render values ~0–60, and possibly canary's own `kernel_display_gamma_type = 2` (BT.709) output stage rather than the game's |
 | T8aD 2D texture | ✅ | `sylpheed-formats/src/t8ad.rs` | **100 % of the disc decodes** (19 216/19 216, measured). The "~15 % deferred variants" were a wrong model, not a variant: a surface is a list of **arbitrary sub-rectangles**, each with a 16-byte header of `dst X, dst Y, width, height`, not a 256×256 grid — `0x1c` is the **rectangle count**. Uncovered area stays transparent. **Colours ✅ CONFIRMED** ([k8888](structures/texture-color-k8888.md)) |
-| RATC bundle | ✅ | `sylpheed-formats/src/ratc.rs` | child listing confirmed. **"One level deep" is not a limitation — there is nothing deeper**: 2 859 bundles hold 18 002 children at depth 1 and **0 at depth 2**, with no parse failures. Nested RATC blobs are **leaf records that reference siblings by name** (`opt `, the sprite name): 3 311 leaves, all embedding sibling names, **10 144 of 10 148 references resolve**. The 4 that do not are one dangling asset — `pmbase.rat` → `pmbase.t32` in `GP_STAGE_CLEAR.pak`'s four language builds, and `pmbase.t32` is **on the disc nowhere** |
+| RATC bundle | ✅ | `sylpheed-formats/src/ratc.rs` | **✅ 2026-08-29: a child's NAME is stated by an `opt ` block** (`"opt " | BE32 len | name | NUL | 3 bytes | magic`), not by the printable bytes before it. We had been guessing it from the last printable run, which is right 17 918 times and **wrong 24**, each time because the 3-byte tail is itself printable — `8AX` (×22) and `'OX` (×2). `8AX` is **not a name**; it hid `pteff05.t32`/`pteff04.t32`, the full-resolution background of all five menu screens, which `compose` then dropped with no diagnostic ([ratc-child-names](structures/ratc-child-names.md)). 🟡 60 of 18 002 children carry no `opt ` block and still use the scan. Child listing confirmed. **"One level deep" is not a limitation — there is nothing deeper**: 2 859 bundles hold 18 002 children at depth 1 and **0 at depth 2**, with no parse failures. Nested RATC blobs are **leaf records that reference siblings by name** (`opt `, the sprite name): 3 311 leaves, all embedding sibling names, **✅ 10 148 of 10 148 references resolve, as of 2026-08-29.** The 4 that did not were `pmbase.rat` → `pmbase.t32` in `GP_STAGE_CLEAR.pak`'s four language builds, recorded as "`pmbase.t32` is on the disc nowhere". It was on the disc all along, as the child the printable-run scan named `8AX` — the `opt ` name fix above resolves it in all four builds (3 686 767 B each). A dangling reference that closes itself when an unrelated decode lands is the corroboration that decode wanted |
 | LSTA sprite list | ✅ | `sylpheed-formats/src/lsta.rs` | A display list of inline elements: **T8aD sprites and `PRMD` primitives**. The `count` at `0x04` is **exact and counts both** — `count == T8aD + PRMD` for **64/64** lists on the disc, which retires the old "a few entries disagree" note (it compared sprites against a total including primitives). **All 1 281 sprite frames decode** after the T8aD rectangle-list fix |
 | IXUD subtitle + caption text | ✅ | `sylpheed-formats/src/ixud.rs` + `movie_subtitle.rs` ([container](structures/idxd-container.md) · [movie link](movie-subtitle-link.md)) | **The IXUD record/field table is decoded and wired in (2026-08-26)** — `IxudObject` mirrors `IdxdObject`; uniform 16-byte records, 12-byte fields, every offset in **chars**, and the word at `0x08` is record 0's hash, not a schema id. Verified disc-wide: **1104/1104** objects, **1476/1476** records, **628 165/628 165** named fields reproducing their `ixud_hash` (`tests/ixud_records_disc.rs`). **Caption text: 537 → 8800 lines, which is 8800 of 8800 distinct keys.** Two steps — generalising the key parser from `MSG_DEMO_*` to all **eight** families (`ACRO ADAN ADPL BIRD DEMO RHIN TCAF` use `MSG_<FAM>_<id>_<page>_<line>`, `VOICE` alone inserts a family letter) took 537 → 8074; switching from **token adjacency to record fields** took it to 8800. ⚠️ An earlier "1.3 % of the game's text" figure of mine counted *occurrences across blocks* — the honest denominator is **8800 distinct keys**, so the real starting point was 6.1 %. The `DEMO` control shows why the field route matters: token adjacency finds 537 lines there, fields find **541** — it was dropping lines in the one family it was written for. | timed cues. **The movie↔subtitle↔voice link is solved — statically**, and as of 2026-08-25 read from the IDXD **record table** rather than scraped from the string pool: **104 cutscene slots binding 101 distinct movies**, 99 slots / 96 movies with a subtitle, 99 / 96 with a voice track, 22 / 22 with a telop. ⚠️ The previous counts (94 / 83 / 21) were the numbers of **distinct pool strings** — a repeat reference contributes no token, so 13 later `VOICE_D_450..454` references read as "no binding". **All 18 hokyu movies are bound**, not five. 93 of the 94 distinct subtitle members resolve; `SUBTITLE_S12B.tbl` resolves in none of the six languages — a dangling reference on the disc. The ~104 **script ids are no longer ❔**: they are literal positional field keys in `BASE_INFO`, each naming its record, and all 104 resolve. `movie_manifest::parse` now reads the record table; CSV regenerated by `examples/movie_map_csv.rs` |
 | Fonts (ttf/otf/ttc) | ✅ | `sylpheed-formats/src/font.rs` | standard OpenType, parsed via ttf-parser |