feat(ui): authored state media animates, so the unseen-text indicator blinks

The blink is not code. It is data, and we were throwing it away.

A retail UI state's media is a small program: images interleaved with timed
pauses, branches, and a terminal hand-off to another state. Our importer kept
the FIRST image per state and dropped the rest, so nothing authored could ever
animate — the indicator was correct in every other respect and simply sat
still.

Measured from the installed dats (LayoutDump --media 0x1000048C), the chat
unseen-text indicator's Normal state authors thirteen steps: two frames
alternating every half second, three times, then `State 13` — Ghosted, whose
authored 0x3B is Invisible.

So retail's indicator is a three-second attention FLASH that hides itself, not
a badge that stays lit until you scroll to the bottom. Nobody would guess that
from the code, because there is no blink code anywhere; the behaviour lives
entirely in the authored sequence. Our shipped version stayed lit, which is
the one thing the data says it must not do.

Sampling is a pure function of (steps, elapsed) rather than a playback object
holding a cursor, so an element only has to remember WHEN its state began and
the whole thing is testable without a clock, a GPU or a frame loop. One shared
UiMediaClock is advanced once per frame by RetailUiRuntime; a UI element has
no tick of its own.

The controller change is the other half: it starts the flash on the rising
edge ONLY. Re-setting Normal every frame would pin the sequence on frame zero
and it would never blink at all — which is the failure mode the second new
test exists to catch, and which no "is it visible?" assertion would notice.
When the sequence reaches its terminal step the controller follows it down
instead of re-lighting it.

Two guesses are refused rather than made, and both are registered: a Pause's
max duration (every sequence measured sets min == max, and what the range MEANS
is not in the decomp) and a sub-1 branch probability (falls through, the
direction where a malformed sequence stops rather than animates forever).
A jump-cycle with no elapsed time is bounded so a bad sequence cannot spin
inside a frame.

Kept `Other` steps in the list rather than filtering them, so a jump's authored
index still lands on the entry it names.

Register: CT-3, CT-4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/AcDream.App/UI/RetailUiRuntime.cs

@@ -851,6 +851,9 @@ public sealed class RetailUiRuntime : IDisposable
 
     public void Tick(double deltaSeconds)
     {
+        // Authored media sequences (a blinking indicator, any cycling element)
+        // are sampled against this one clock — UI elements have no tick.
+        Layout.UiMediaClock.Advance(deltaSeconds);
         FpsController?.Tick();
         _vividTargetIndicator?.Tick();
         _vitalsSideBySide?.Tick();