re(ui): the focus ring SPINS, the game draws it, and the leaf owns the f record

Three things, all from parsing ptbtn0Nf.rat as a build.

1. THE RING SPINS. Its two keyframes differ in exactly one field: rotation_deg
ramps 0 -> 360 with position, scale, alpha and tint all constant. A spin in
place, the same shape as the GP_BUNK example already recorded.

2. THE ORACLE CONFIRMS THE GAME RENDERS IT. In the OPTIONS-focused capture the
ring's bright head sits in a completely different angular position from the
sprite's own -- caught mid-spin. This is a SECOND independent confirmation that
rotation_deg is drawn, now on a different screen and a different element from the
ptloop sweeps, and it raises rotation's priority: it is not a title-only concern
that sits off-screen at rest, it is the main menu's focus marker.
NO ANGLE IS QUOTED. A brightest-region centroid says ~250 deg, but the control
refuses that precision -- rotating the sprite by a known 30/90/180/270 and
re-measuring gives errors up to 19.8 deg. What survives the error bar is that a
<=20 deg error cannot manufacture a ~250 deg displacement.

3. WHICH PLACEMENT WINS -- correcting this page's own earlier caveat, which said
to use the leaf only for elements the parent does not declare. Right for a BASE
record, wrong for an f record: the parent declares NO element for ptbtn0Nf.rat at
all (zero of build 5's 16), so the f record's placement comes from its leaf for
BOTH elements, label included. The label's (-7,-7) is load-bearing -- the f
sprite is 13px larger per axis and -7 keeps them concentric (535+96/2 = 583 vs
542+83/2 = 583.5). Corroborated against the oracle: the focused-minus-unfocused
region is x 505..703, and the leaf predicts a right edge near 707 where the
parent reading predicts 714.

Also exposes UiBuild::records (name -> (offset, size) of a nested .rat leaf).
Nested records were parsed into a PRIVATE map, so a consumer holding a UiBuild
could not locate a leaf's bytes at all -- which is exactly what blocked the port
from reaching the ring.

crates/sylpheed-formats/examples/rat_leaf_placement.rs

@@ -55,6 +55,13 @@ fn main() {
                             r.map(|k| k.y).unwrap_or(-1),
                             el.keyframes.len()
                         );
+                        for (i, k) in el.keyframes.iter().enumerate() {
+                            println!(
+                                "            kf{i}  t={:?} pos=({},{}) scale={}%,{}% a={} rot={} tint={:#010x}",
+                                k.time, k.x, k.y, k.scale_x, k.scale_y,
+                                k.fade >> 24, k.rotation_deg, k.tint
+                            );
+                        }
                     }
                 }
             }

crates/sylpheed-formats/src/ui_layout.rs

@@ -322,6 +322,20 @@ pub struct UiBuild {
     pub elements: Vec<Element>,
     /// Sprite name → (offset, size) of its `T8aD` child within the bundle.
     pub sprites: HashMap<String, (usize, usize)>,
+    /// Record name → (offset, size) of its nested `.rat` **leaf** within the
+    /// bundle, e.g. `ptbtn01f.rat`.
+    ///
+    /// Exposed because a leaf is where a focused button's extra elements live —
+    /// `ptbtn0Nf.rat` declares the focus ring `ptbtneff01.t32` **and** the bright
+    /// label, and the parent bundle declares no element for the `f` record at
+    /// all. A consumer that walks only top-level elements cannot see either.
+    ///
+    /// A leaf is itself readable by [`parse_build`]: its first 32 bytes have the
+    /// same shape as a bundle header, so
+    /// `parse_build(&bundle[off..off + size])` returns its elements with
+    /// absolute design-space placements. See
+    /// `docs/re/structures/ui-button-focus-record.md`.
+    pub records: HashMap<String, (usize, usize)>,
     /// A guessed context from the sprite naming (e.g. `"tutorial"`), if any.
     pub context_hint: Option<String>,
     /// True when the declaration table was unusable and the build was recovered
@@ -599,6 +613,7 @@ pub fn parse_build(bundle: &[u8]) -> Option<UiBuild> {
         design_h,
         elements,
         sprites,
+        records,
         context_hint,
         from_fallback,
         placement_order,