ops: finalize production domain and hardware benchmark tooling

Add /version.json build identity, deploy 16e7930 release markers,
DNS/Named Tunnel prep docs, portable browser benchmark, and replay
stability probe. Keep Quick Tunnel until permanent domain cutover.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -3,6 +3,13 @@ WORKDIR /app
 COPY package*.json ./
 RUN npm ci
 COPY . .
+# .git is dockerignored — pass identity from host deploy script
+ARG BUILD_COMMIT=unknown
+ARG BUILD_BRANCH=unknown
+ARG BUILD_RELEASE=unknown
+ENV VITE_BUILD_COMMIT=$BUILD_COMMIT \
+    VITE_BUILD_BRANCH=$BUILD_BRANCH \
+    VITE_BUILD_RELEASE=$BUILD_RELEASE
 RUN npm run build
 
 FROM nginx:alpine AS runtime