re: enumerate an element's records; focus_link is a misnomer

Adds examples/element_records.rs, which lists leaf AND focus_link records
for an element, plus a disc-wide census. Built because I claimed alpha 80
was undeclared after reading one of ptbtn00's two records -- and focus_link
was already parsed, with ui_layout.rs:424 already documenting the focus
record. The format was known and I did not consult it.

Census: 1467 of 15493 elements (9.5%) across 815 builds carry a second
record whose keyframes are invisible to a by-name leaf lookup.

Refutes our own parser's description of the field. It is documented as "the
focused state of a button", but GP_TITLE has pgloading_loop1 -> loop3 ->
loop4, a chain of three loop animations, and ptloop01 -> ptloop02, the two
sweeps. Neither is a focused state. Naming defect only -- behaviour is right
where it is read -- so not renamed here.

🟡 Notes a better candidate for why the two sweeps share one indices=8 draw:
they are linked, not merely co-textured. Testable on the pgloading chain,
which needs a loading-screen capture I do not have. Named, not claimed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jc4pciRArGHfxGGhEbwp5t

docs/re/element-records-enumerated.md

@@ -0,0 +1,75 @@
+# Enumerating an element's records — and `focus_link` is a misnomer
+
+**Question:** how many records does a UI element actually have, and does my
+tooling see them all?
+
+**What the human looks at:** run
+`cargo run -p sylpheed-formats --example element_records -- GP_TITLE ptbtn00`.
+Pass = **two** records listed. Fail = one.
+
+**What this does NOT cover:** F5's code route, the `0x70000` bits.
+
+**Instrument:** ⟨disc⟩, every `.pak`.
+
+## Why
+
+I claimed `ptbtn00f`'s α80 was undeclared, having read `ptbtn00.rat` — the leaf,
+flat α255 — and stopped. The pulse is in `ptbtn00f.rat`, reached by `focus_link`.
+**`focus_link` was already parsed, and `ui_layout.rs:424` already documented that
+`ptbtn0Nf.rat` carries the focus ring.** The format was known; I did not consult
+it. So this enumerates rather than asking the next reader to remember:
+
+```
+entry 2: ptbtn00.rat
+   leaf   ptbtn00.rat    loop 120  ptbtn00.t32  [1 keys, peak a255]
+   focus  ptbtn00f.rat   loop 120  ptbtn00f.t32 [8 keys, peak a80]
+```
+
+The fact I missed is the second line.
+
+## ✅ Census — how much of the corpus this exposes
+
+| | |
+|---|---|
+| elements disc-wide | **15 493** |
+| carrying a second record | **1 467 (9.5 %)** |
+| builds containing at least one | **815** |
+
+Every one of those has keyframes invisible to anyone who looks a leaf up by name
+and stops.
+
+## 🔴 `focus_link` is the wrong name for at least some of its uses
+
+The parser calls it *"`opt ` link to another record — the focused state of a
+button"*. On `GP_TITLE` that description fails twice:
+
+```
+pgloading_loop1 --> pgloading_loop3 --> pgloading_loop4
+   (300 units)        (120 units)         (360 units)
+ptloop01        --> ptloop02
+   (600 units)        (720 units)
+```
+
+A **chain of three loop animations**, and **the two sweeps**. Neither is a
+focused button state. The field links records; "focus" is one thing it is used
+for, not what it means.
+
+Recorded as a naming defect in our own parser, not corrected here — the field's
+*behaviour* is right everywhere it is read, and renaming it touches every caller.
+
+## 🟡 A candidate mechanism for the batched draw
+
+The two sweeps arrive in a **single `indices=8` draw**
+([`f6-unit11`](f6-unit11-pteff03a-IS-drawn.md)), which I have been treating as
+"they share a texture page". They are also **linked** — `ptloop01 → ptloop02`.
+That is a better candidate explanation, and it is testable: another linked pair
+should batch too.
+
+**Not tested.** The obvious subject is the `pgloading` chain, and I have no
+loading-screen capture. Recorded as 🟡 with the experiment named, not as a
+finding.
+
+## Reach
+
+The census counts `focus_link` only. If a record can be reached by any *other*
+route, this enumeration is still incomplete and the census is a lower bound.