feat(dashboard): iter B+C+D+E+F — sim controls, scene toolbar, seed modal, transport-pill click, sidebar tunables wire-through, SNR, prefers-reduced-motion auto-detect, REPL proof.export

Closes ADR-093 P0.5, P0.6, P0.7, P0.9, P1.4, P1.8, P1.10, P1.11.

## Iter B — scene toolbar + sim controls (P0.6, P0.7)
- nv-scene scene-toolbar (top-left): zoom +/-, fit-to-view, layer
  toggles for sources / field lines / labels. Zoom drives the SVG
  viewBox so the entire scene scales uniformly.
- nv-scene sim-controls (bottom-right): step ⏮ / play ▶ / step ⏭ /
  speed cycle (0.25× → 4×). Bound to client.run/pause/step.

## Iter C — topbar pill clicks (P0.5, P1.10)
- Seed pill click opens a "Set seed" modal with a hex-validated input.
  Apply propagates via WasmClient.setSeed and toasts the new value.
- Transport pill (wasm/ws) click opens the Settings drawer (Transport
  section), letting the user switch modes inline.

## Iter D — sidebar tunables wire-through (P1.8)
- Every slider edge-triggers pushConfigDebounced() (300 ms). The
  debounced call forwards { digitiser: { f_s_hz, f_mod_hz }, sensor: {
  …, shot_noise_disabled }, dt_s } to the worker via setConfig RPC.
  Worker rebuilds the WasmPipeline so the running stream picks up the
  new config without restart.

## Iter E — proof.export REPL command (P0.9)
- nv-console adds proof.export → calls client.exportProofBundle() and
  triggers a download of the resulting JSON manifest with a timestamp
  filename. Listed in `help`.

## Iter F — SNR + prefers-reduced-motion (P1.4, P1.11, P1.3)
- nv-scene now computes SNR per frame as |b| / max(sigma_per_axis) and
  publishes to the snr signal. The corner stat-card stops showing "—".
- main.ts honors the system prefers-reduced-motion as the default for
  motionReduced when no IndexedDB override is set.

ADR-093 §2/§3 updated to mark these P0/P1 items resolved.

Co-Authored-By: claude-flow <ruv@ruv.net>

dashboard/src/main.ts

@@ -26,7 +26,8 @@ function applyMotion(reduced: boolean): void {
   // Restore persisted prefs
   const t = (await kvGet<'dark' | 'light'>('theme')) ?? 'dark';
   const d = (await kvGet<'comfy' | 'default' | 'compact'>('density')) ?? 'default';
-  const m = (await kvGet<boolean>('motionReduced')) ?? false;
+  const sysMotion = window.matchMedia?.('(prefers-reduced-motion: reduce)').matches ?? false;
+  const m = (await kvGet<boolean>('motionReduced')) ?? sysMotion;
   theme.value = t; applyTheme(t);
   density.value = d; applyDensity(d);
   motionReduced.value = m; applyMotion(m);