Specs rendering the casa_app layout fail locally: tailwind.css was not declared to be precompiled

What happens

On a fresh local checkout, any spec that renders the casa_app layout fails:

Sprockets::Rails::Helper::AssetNotPrecompiledError:
  Asset `tailwind.css` was not declared to be precompiled in production.
  Declare links to your assets in `app/assets/config/manifest.js`.

    //= link tailwind.css

  and restart your server
  ./app/views/layouts/casa_app.html.erb:15

For example, three examples in spec/requests/case_court_reports_spec.rb (the index action):

rspec ./spec/requests/case_court_reports_spec.rb:14  # as volunteer can view 'Generate Court Report' page
rspec ./spec/requests/case_court_reports_spec.rb:28  # as a supervisor can view the 'Generate Court Report' page
rspec ./spec/requests/case_court_reports_spec.rb:37  # as a supervisor with no cases in the organization

CI is green — .github/workflows/rspec.yml runs bundle exec rails assets:precompile in its Build App step, so app/assets/builds/tailwind.css exists there. This is purely a local developer experience problem, but it hits anything rendering a casa_app page, which is a growing share of the app as the design migration proceeds.

Why

app/assets/builds/tailwind.css does not exist until someone builds it. Before #7071 ("disable on-demand asset compilation") Sprockets would compile on demand and this worked; now it is a hard failure.

The error message is actively misleading — it tells you to declare the asset in app/assets/config/manifest.js, but the manifest is already correct:

//= link_directory ../builds .css

link_directory only picks up files that exist. The real problem is that nothing has written tailwind.css yet.

Two things worth fixing

1. Document it. Neither the README nor bin/setup mentions that you must build CSS before running specs. npm run build only builds JS — CSS is a separate npm run build:css. Easy to miss, and the resulting error points you at the wrong file.

2. npm run build:css may not work. On my machine it fails outright:

$ npm run build:css
> tailwindcss -i ./app/assets/stylesheets/tailwind.css -o ./app/assets/builds/tailwind.css --minify
sh: tailwindcss: command not found

package.json declares both tailwindcss and @tailwindcss/cli at ^4.3.2, but after npm install, node_modules/@tailwindcss/ is empty and there is no node_modules/.bin/tailwindcss. In Tailwind v4 the CLI binary comes from @tailwindcss/cli, so the script may need to be npx @tailwindcss/cli — or this is an install/lockfile problem specific to my machine (arm64 macOS). Flagging it as an observation rather than a diagnosis; someone should check whether a clean npm ci produces a working tailwindcss binary before changing the script.

Suggested fix

• Have bin/setup build CSS alongside JS, and/or add a line to the README's testing section
• Confirm npm run build:css works from a clean npm ci, and fix the script if not
• Optionally, make the failure self-explanatory — a clearer message than Sprockets' default would save the next person the detour through manifest.js

Context

Found while debugging #7093 — these three failures were initially mistaken for fallout from that work before being traced to missing built assets.

Start with package.json, bin/setup, the README testing section, and app/assets/config/manifest.js. Run npm ci followed by npm run build:css, then reproduce a listed case_court_reports_spec.rb example to verify the local setup. Done means the CSS build works cleanly and setup or documentation prevents casa_app specs from failing because tailwind.css is absent.