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/METHOD.md

@@ -838,3 +838,22 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
   "measured" covers several kinds of evidence, and the page that recorded it
   usually says which — `ui-screen-runtime.md` said "child slots" in as many
   words. Read that line before building an argument on top of it.
+
+* **A heuristic that is right 99.9 % of the time still has a shape to its
+  failures — find it before trusting the field.** RATC child names were read by
+  scanning backwards for the last printable run of bytes. That agrees with the
+  format's own `opt ` declaration on 17 918 of 17 942 children, which is the kind
+  of agreement that stops people looking. The 24 exceptions were not random: all
+  24 are the *same* case, a 3-byte binary tail that happens to be printable ASCII
+  (`8AX`), and one of them was the full-resolution background of every menu
+  screen we care about. Ask what the format *states* before settling for what a
+  scan *infers*, especially when the stated version is already decoded elsewhere
+  in the same file — `opt ` was being read for button focus links the whole time.
+
+* **A `continue` that silently skips is a defect even when the skip is correct.**
+  `compose` drops an element whose sprite does not resolve. Two arms above it
+  record the name into `missing` first; the `el.sprite.is_none()` arm does not.
+  So a screen lost its background and `screen render` still reported "sprites
+  that did not resolve: none" — the diagnostic was structurally unable to see it.
+  When adding an early-out to a loop that already reports what it discards, make
+  it report through the same channel, or it becomes a place findings go to die.