Stop stale dev builds.

The 90-second order of operations

Do the cheap checks before deleting half your project.

1. 1
   Prove whether it is browser state.
   Open a clean profile/incognito, disable cache while DevTools is open, and unregister service workers.
2. 2
   Prove whether the server sees files.
   Touch a source file and watch terminal rebuild output. If nothing logs, fix file watching first.
3. 3
   Prove whether env is embedded.
   Client env is compiled into bundles. Change env, fully restart, then rebuild if needed.

Pasteable Docker watcher baseline

services:
  web:
    environment:
      WATCHPACK_POLLING: "true"
      CHOKIDAR_USEPOLLING: "true"
      # Optional if CPU is high:
      WATCHPACK_POLLING_INTERVAL: "300"
    volumes:
      - .:/app
      - /app/node_modules

CI cache key sanity pack

Preview builds that disagree with local often share one bad cache key across OS, Node, package manager, or lockfile changes.

- uses: actions/setup-node@v4
  with:
    node-version-file: .nvmrc
    cache: npm
    cache-dependency-path: package-lock.json

# Cache key checklist:
# include runner.os, Node version, package manager, and lockfile hash
# never restore node_modules from a branch with a different lockfile