re(ui): decode keyframe +12 as screen-plane rotation in degrees

The rotated quads on the title screen come from the keyframe block after
all. The earlier negative -- "every GP_TITLE build 4 element has all three
angle words at zero" -- read the right bytes over too small a region: it
walked the top-level declaration table, and the rotated elements are the
nested leaf records ptloop01.rat / ptloop02.rat.

Confirmed against the framebuffer rather than against our own renderer.
The two records declare +12 = 30 and -45; the GPU capture submits their
quads at +30.26 and -45.28 degrees -- magnitude and sign, two different
values. Corroborated by shape in GP_BUNK 117ca14f, where +12 ramps
0 -> 360 with position, scale and alpha constant: a spin in place.

Identifying which draw it was needed edge lengths, not bounding boxes:
400x1076 and 400x1444 against pteff03/pteff03a 399x180 at the elements'
two different declared scales, 600% (1080) and 800% (1440). The same test
names three known-positives in the capture (ptlogo1, ptcopyright,
ptbtn00), so it passes its own control.

Keyframe gains rotation_deg plus unknown_4/unknown_8, carried rather than
dropped. NOT rendered -- ui_layout::blit is axis-aligned only, so the
reference renderer and the port will both draw these upright until a
rotating blit exists.

The census tool ships with the trap that broke its first version: nested
RATC blobs are not 4-byte aligned, so an aligned scan found 0/3 of its
own control blocks and missed 16 341 blocks. Disc-wide +12 is non-zero in
14.50 % of 83 862 blocks.

sylpheed-formats tests, SYLPHEED_DISC set: 131 passed, 0 failed across the
6 suites finished at commit time; the run had not yet completed.

crates/sylpheed-cli/src/main.rs

@@ -523,7 +523,7 @@ fn print_geometry(b: &sylpheed_formats::ui_layout::UiBuild, bytes: &[u8]) {
     println!();
     println!("geometry — decoded sprite size vs the declared pivot, and every keyframe");
     println!(
-        "{:<3} {:<26} {:>11} {:>11} {:>5}  keyframes  t: x,y sx%,sy% a=fade-alpha",
+        "{:<3} {:<26} {:>11} {:>11} {:>5}  keyframes  t: x,y sx%,sy% a=alpha r=rot°",
         "#", "sprite", "decoded", "pivot*2", "same"
     );
     for el in &b.elements {
@@ -543,8 +543,13 @@ fn print_geometry(b: &sylpheed_formats::ui_layout::UiBuild, bytes: &[u8]) {
             .keyframes
             .iter()
             .map(|f| {
+                let rot = if f.rotation_deg != 0 {
+                    format!(" r={}", f.rotation_deg)
+                } else {
+                    String::new()
+                };
                 format!(
-                    "{}: {},{} {}%,{}% a={}",
+                    "{}: {},{} {}%,{}% a={}{rot}",
                     f.time.map(|v| v.to_string()).unwrap_or_else(|| "-".into()),
                     f.x,
                     f.y,