t8ad: a surface is a list of sub-rectangles, not a 256 grid -- disc decode 96% -> 100%

The "~15% deferred variants" were not variants. Auditing every T8aD on the disc
gave 19216 surfaces, 18442 decoding (96.0%) and 774 failing in two clusters:
GP_DIALOG strips declaring 524x63 with a "tile count" of 1 or 2 instead of 3, and
small textures in the six *2D language paks whose pixels ran past the end of the
file.

Both fall out of the per-tile header, which is not opaque flags: it is four BE
u32 -- dst X, dst Y, width, height. A 15x18 icon stores a 13x18 rectangle at
(1,0); pdmes010 stores (59,6,256,54) and (315,6,149,54), the second beginning
exactly 16 + 256*54*4 bytes after the first. So 0x1c is a RECTANGLE COUNT and the
256-grid reading was an accident of most surfaces being stored as full-width
bands.

Parser rewritten to that model, still refusing to guess: a rectangle must fit the
declared surface and its pixels must fit the file, else None. Disc decode is now
19216/19216 = 100.00%.

Two test fixtures were built to the old model and are corrected rather than
worked around. lsta's t8ad_frame wrote NO offset-table entry, so the decoder read
"pixels" from inside the header -- the test passed only because it checked
dimensions alone.

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

docs/re/INDEX.md

@@ -14,7 +14,7 @@ Promote to a prose `structures/…md` file when a format needs behavioural notes
 | name-hash (TOC keys) | ✅ | `sylpheed-formats/src/hash.rs` | Barrett-reduction hash; recovers original paths |
 | IDXD object/table | ✅ | `sylpheed-formats/src/idxd.rs` | self-describing; ship/weapon stats verified vs known values |
 | 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 ❔ |
-| T8aD 2D texture | 🟡 | `sylpheed-formats/src/t8ad.rs` | ~85% decode; **colours ✅ CONFIRMED** ([k8888](structures/texture-color-k8888.md)); ~15% variants deferred |
+| 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 |
 | LSTA sprite list | 🟡 | `sylpheed-formats/src/lsta.rs` | inline T8aD frames |
 | IXUD subtitle | 🟡/✅ | `sylpheed-formats/src/ixud.rs` + [movie link](movie-subtitle-link.md) | timed cues. **The movie↔subtitle↔voice link is solved — statically**, from the movie config record in `tables.pak` (schema `0x067025b9`), not from the running game as this row previously assumed: [101 movies mapped](captures/movie-subtitle-voice-map.csv), 94 with subtitles, 83 with voice, 21 with a telop overlay. 93 of 94 subtitle refs resolve in the language paks; **`SUBTITLE_S12B.tbl` is missing from all six languages** — a dangling reference on the disc. Naming is `SUBTITLE_<base>.tbl` / `VOICE_<base>` with six documented exceptions. The record's ~104 **script ids** are ❔ — positional pairing drifts by three because the IDXD pool dedupes repeated values |