feat(nvsim): server + onboarding + PWA + GH Pages workflow [ADR-092]

Rounds out the dashboard surface introduced in 39ec05edc with all four
remaining ADR-092 deliverables, plus a deploy workflow that publishes
the SPA to gh-pages/nvsim/ without disturbing the existing observatory
or pose-fusion demos.

## nvsim-server (ADR-092 §6.2)

New crate `v2/crates/nvsim-server`. Axum host fronting nvsim::Pipeline:

- REST control plane (15 routes) — /api/health, /api/scene, /api/config,
  /api/seed, /api/run, /api/pause, /api/reset, /api/step,
  /api/witness/{generate,verify,reference}, /api/export-proof
- Binary WebSocket data plane at /ws/stream — pushes 32-frame
  MagFrame batches at ~60 Hz tick rate
- /api/witness/verify always runs the canonical Proof::generate so the
  hash matches Proof::EXPECTED_WITNESS_HEX byte-for-byte across WASM
  and WS transports — the determinism contract.
- CORS configurable via --allowed-origin, listens on 127.0.0.1:7878 by
  default, single-binary deployment.

## Onboarding tour (ADR-092 §10 Pass 6)

`<nv-onboarding>` Lit component, 6-step welcome:
  Welcome → Scene canvas → Run → Witness → App Store → Done.
First-run only — persisted via IndexedDB `onboarding-seen` flag.
Re-triggerable via `nv-show-tour` event for the help menu.

## PWA service worker (ADR-092 §9.3)

vite-plugin-pwa wired with workbox-window. autoUpdate registration,
8 MB precache budget, app-shell + WASM caching:
- manifest.webmanifest with /RuView/nvsim/ scope
- icon-192.svg + icon-512.svg in dashboard/public/
- 16 precache entries / 302 KiB

Verified production build under NVSIM_BASE=/RuView/nvsim/:
  dist/index.html → /RuView/nvsim/assets/...
  dist/manifest.webmanifest → scope: /RuView/nvsim/
  dist/sw.js + workbox-*.js generated cleanly

## GitHub Pages deploy workflow

`.github/workflows/dashboard-pages.yml`:
- Triggers on push to main affecting dashboard/ or v2/crates/nvsim/
- Builds wasm-pack release → npm ci → vite build with prod base path
- Deploys to gh-pages/nvsim/ via peaceiris/actions-gh-pages@v4 with
  keep_files: true — preserves observatory/, pose-fusion/, and the
  root index.html landing page

After first run, the dashboard will be live at:
  https://ruvnet.github.io/RuView/nvsim/

Validated end-to-end with `npx agent-browser`:
- Onboarding modal renders on first visit
- Workspace `cargo check --workspace` clean (1 warning in unrelated
  sensing-server, no nvsim-server warnings after dead-code prune)
- Production build passes with correct base path resolution and
  PWA manifest scope

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

dashboard/public/icon-192.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 192 192" width="192" height="192">
+  <rect width="192" height="192" rx="36" fill="#e6a86b"/>
+  <text x="96" y="124" text-anchor="middle" font-family="ui-monospace,SFMono-Regular,Menlo,monospace" font-weight="700" font-size="80" fill="#1a0f00">NV</text>
+</svg>

dashboard/public/icon-512.svg

@@ -0,0 +1,10 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="512" height="512">
+  <defs>
+    <linearGradient id="g" x1="0" x2="1" y1="0" y2="1">
+      <stop offset="0" stop-color="#e6a86b"/>
+      <stop offset="1" stop-color="#a4633a"/>
+    </linearGradient>
+  </defs>
+  <rect width="512" height="512" rx="96" fill="url(#g)"/>
+  <text x="256" y="332" text-anchor="middle" font-family="ui-monospace,SFMono-Regular,Menlo,monospace" font-weight="700" font-size="220" fill="#1a0f00">NV</text>
+</svg>