Give staging its own address rather than a spare room in the main house

A subdomain means a separate origin, so a staging run can no longer overwrite
the localStorage the testteam is playing on. That makes the /staging alias
pointless, so the Dockerfile goes back to exactly what is deployed today.

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

Dockerfile

@@ -1,14 +1,9 @@
 FROM nginx:alpine
 # no-cache => browsers revalidate every request (ETag 304s are cheap), so a new
 # deploy is picked up on plain reload. ponytail: switch to hashed filenames if traffic ever matters.
-# nginx's default map has no .webmanifest entry and Chrome refuses to install a homescreen app
-# served as octet-stream, so we append the type to the stock map. It has to be the map and not a
-# `location`: an exact match misses the /staging/ copy below, and a regex match would out-rank the
-# /staging/ prefix and resolve against root instead of the alias. A local `types {}` block is out
-# too — it REPLACES the whole map (breaking .js/.png), and mime.types can't be re-included inside one.
-RUN sed -i 's#^}#    application/manifest+json  webmanifest;\n}#' /etc/nginx/mime.types
-# The /staging/ alias serves the SAME files one level down, so the staging deploy works whether or
-# not Coolify/Traefik strips the path prefix. Identical on every branch => never a merge conflict.
-RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  etag on;\n  index index.html;\n  absolute_redirect off;\n  location = /staging { return 301 /staging/; }\n  location /staging/ { alias /usr/share/nginx/html/; add_header Cache-Control "no-cache, must-revalidate"; }\n  location / { add_header Cache-Control "no-cache, must-revalidate"; }\n}\n' > /etc/nginx/conf.d/default.conf
+# The exact-match location gives the manifest its own MIME type — nginx's default map has no
+# .webmanifest entry and Chrome refuses to install a homescreen app served as octet-stream.
+# (a bare `types {}` block would have REPLACED the whole map and broken .js/.png too.)
+RUN printf 'server {\n  listen 80;\n  root /usr/share/nginx/html;\n  etag on;\n  location = /manifest.webmanifest { default_type application/manifest+json; add_header Cache-Control "no-cache, must-revalidate"; }\n  location / { add_header Cache-Control "no-cache, must-revalidate"; }\n}\n' > /etc/nginx/conf.d/default.conf
 COPY index.html manifest.webmanifest *.js /usr/share/nginx/html/
 COPY assets /usr/share/nginx/html/assets

HANDOFF.md

@@ -23,11 +23,10 @@ the primary target.
   a push. **Bump `main.js?v=N` in index.html every time** or phones keep the old build.
   The Dockerfile must also COPY any new top-level file (it currently ships `index.html`,
   `manifest.webmanifest`, `*.js`, `assets/`).
-- **Staging**: the `staging` branch deploys to splatter-tennis.wuwi.one/staging (own Coolify
-  resource, same repo, branch `staging`). Test there first, then merge to `main` for the testteam.
-  The branch carries NO diff against main — the image serves the app at both `/` and `/staging/`,
-  so it can be fast-forwarded and merged freely. Note it shares the origin (and therefore
-  localStorage) with prod.
+- **Staging**: the `staging` branch deploys to its own subdomain (own Coolify resource, same repo,
+  branch `staging`, same Dockerfile). Test there first, then merge to `main` for the testteam.
+  The branch carries NO diff against main, so it fast-forwards and merges freely — keep it that way.
+  A subdomain, not a subfolder, so staging gets its own origin and can't stomp the prod localStorage.
 - **Oliver edits files himself** (tuning values, sometimes sprites). ALWAYS Read current file state
   before editing; never assume your last version is what is on disk.