fix(tui): the wave blooms from the center, the figure stops blinking [spec 10]

[wine-fall]

Implements specs/spec10/10-tui.md (§3.6 visualizer, §6.1 quiet-constellation).

Two by-eye reports from the first real Ghostty session after #115.

Wave direction

The spectrum bins were laid left-to-right across the arc, so bin 0 — the
bass, which is almost always breathing — anchored the left arm and the wave
read as growing from the left edge. waveBinAt now mirrors the spectrum
from the arc's middle outward: bass rises at the center, treble frays toward
both arms, and the wave blooms symmetrically. Unit-tested for mirror
symmetry and for a bass-only frame lighting only the center.

Start-of-broadcast flash

The raster figure's placement effect depended on the pose, so the first
spoken line (greeting -> talk) tore the effect down: deleteFigures, then a
600ms resettle before the repaint — the figure blanked visibly on every
state change. The pose now rides a ref and swaps the next transmitted frame
in place under the same kitty image id; PNGs are encoded per pose on first
use, a shared clock advances each pose at its own fps, and identical frames
are not retransmitted. Only a real relayout (resize, breakpoint, settings)
tears the placement down.

Acceptance

Wide-pty harness (200x50, ghostty env, STUB): 73 in-place frame
retransmissions across a 22s run spanning the greeting->talk transition,
zero a=d deletes before shutdown — the flash's byte signature is gone.
Full suite 688 green; typecheck and lint clean.

Peer review (codex gpt-5.5 xhigh): 0 findings.

AI coding brief

• Original request: two visual defects from a real listening session —
  the figure flashes once when the radio's first line arrives, and the wave
  always grows from the left instead of emanating from the center.
• Manual interventions: none this round; both root causes were readable
  from the code, no added logging needed.
• Retro: effect dependency lists are where TUI flicker hides — anything
  that deletes a terminal-side artifact on re-run must depend only on real
  layout inputs, with content swaps riding refs.

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