re(ui): the 60 nameless RATC children are frames, not children -- .tan decoded

Closes the reach caveat the `opt ` name fix left behind: 60 of 18 002 RATC
children carry no `opt ` block, and it was not established whether they lack one
or sit past our 128-byte window.

Neither. They are not children. `examples/ratc_optless_children.rs` re-runs
`ratc::parse`'s own guards over the disc and reports which one fired: all 60 are
"tag beyond the window", none is rejected by length, gap or charset, none is
child #0, and all 60 live in six bundles of one archive. Within a bundle the
distances back to the nearest tag are an exact arithmetic progression, step
60 600 -- ten different records finding the SAME tag, because there is only one.

Reading a bundle directly: children 1..10 are equal-size T8aD blocks under a
single `opt ` name, `pb_f15_eg_anm.tan`. `.tan` is a FRAME SEQUENCE. One block
declares the resource; its payload is a run of T8aD frames.

Disc-wide, over all 18 718 `opt ` names in all 33 paks: a RATC bundle names
exactly six kinds of resource -- `.t32` 14 756, `.rat` 3 311, `.prm` 367,
`.tbm` 224, `.sbo` 54, `.tan` 6. Six `.tan`, ten frames each = 60, the entire
population with nothing left over. The negative is closed, not narrowed.

Consequence recorded but deliberately not fixed: `ratc::parse` over-reports
there, listing a `.tan`'s frames as anonymous children. Nothing in the menu
milestone reads a `.tan` -- it occurs only in GP_READY_ROOM, which S1 ruled
out -- so no screen the port draws changes.

Also a METHOD entry for this container OOM-killing `slb_leading_segment_disc`
under default test parallelism (SIGKILL, no assertion; 8/8 pass with
--test-threads=1).

docs/port/HANDOFF.md

@@ -278,6 +278,17 @@ authored version can be deleted.
   it): correct, but wasted fill. Draw only the full-res one, taking its *timing*
   from `ptbase`'s element, which carries the keyframes.
   [`structures/ratc-child-names.md`](../re/structures/ratc-child-names.md)
+  ✅ **And the fix has no remaining hole.** 60 of the disc's 18 002 RATC children
+  still have no `opt ` block; all 60 are now accounted for and **none is on your
+  screens**. They are the ten frames of the disc's only `.tan` **frame sequence**
+  (`pb_f15_eg_anm.tan`, six language copies of one `GP_READY_ROOM` bundle), where
+  a single `opt ` block names the whole run — so a name-resolution miss is not
+  hiding anything else the way `8AX` was. ⚠️ Two notes if you ever read outside
+  `GP_TITLE`: `ratc::parse` **over-reports** there, listing a `.tan`'s frames as
+  anonymous children; and a RATC bundle names exactly six kinds of resource —
+  `.t32` (14 756), `.rat` (3 311), `.prm` (367), `.tbm` (224), `.sbo` (54),
+  `.tan` (6).
+  [`structures/ratc-tan-frame-sequence.md`](../re/structures/ratc-tan-frame-sequence.md)
   <details><summary>the original entry, kept because its reasoning still stands</summary>
 
   🟡 **`screen render` silently drops one full-screen element per screen — and