feat: sign interlude, window plate and a two-button control bay

The sign closes in over the road on a gantry truss, arcs into a wider
window and hands off to a flat 2D plate that mirrors its face; content
steps aside for the interlude and rises after. The bay keeps sound and
settings; volume and Pause motion move into the settings popover.

docs/redesign/round5.md

@@ -110,3 +110,36 @@ content had to stay out of their way.
     it, so no light ever passes the car.
   - A unit test pins both rules.
   - The car's own lamps and the wake stay parented to the car, as before.
+
+## Evidence
+
+All captures are 1440x900 unless named otherwise, from the production
+preview build on a headed GPU Chromium. They are in `docs/redesign/round5/`.
+
+| Item | Before | After |
+| --- | --- | --- |
+| 4, 5, 6, 8 Gantry | `gantry-before-1440.webp` | `gantry-after-1440-incoming.webp`, `-docked.webp`, `-idle.webp`, `gantry-after-1024.webp`, `gantry-after-390.webp` |
+| 1 Outro | `outro-before-1440.webp` | `outro-after-1440.webp` |
+| 7 Car | left half of `car-before-after-desktop.webp` | right half; `car-lite-390.webp` |
+| 9, 10 Cards and motion | `cards-before-1440.webp` | `cards-after-1440.webp` |
+
+- **Gantry docking (headed run, clicking Profile).** idle at 300 ms,
+  incoming at 700 ms, docked from 1000 to 2600 ms, passing at 3300 ms, idle
+  at 3700 ms. The face lands within 2 px of the window at 1440x900,
+  1920x1080, 1024x768, 390x844 and 844x390 (unit tests). Clicking the
+  window, or Enter on it, drives to the next exit (Start to Profile, then
+  Experience) at 1440 and 390.
+- **A mask bug found on the way.** The window cut-out used `--window-x`
+  as a `mask-position`. Percentages there resolve against the box minus the
+  layer, so the hole sat 128 px left of the window and the beam hid half of
+  the sign. The cut-out now has its own `--window-mask-x`.
+- **Car.** Phones and the low tier load the lite model: 31,288 to 11,027
+  faces, 1.19 MB to 0.50 MB raw. The transfer saving is small (149 KB to
+  143 KB), because the geometry already compresses well. The real wins are
+  parse time and GPU memory.
+- **fps (same machine, same script, Intel Arc iGPU, headed).**
+
+  | | start | infrastructure | builds | toolkit | contact |
+  | --- | --- | --- | --- | --- | --- |
+  | Before | 70.1 | 82.6 | 83.8 | 81.8 | 87.2 |
+  | After | 68.7 | 83.5 | 79.7 | 83.7 | 95.1 |