Pin the npm upgrade task to @tailwindcss/upgrade@4.1.4

[flavorjones]

We're pinning to v4.1.4 because v4.1.5 of the upgrade tool introduces a dependency version check on tailwind and I haven't been able to figure out how to get that to work reliably and I am extremely frustrated with the whole thing.

The error we're seeing in CI and in development with v4.1.5:

run npx @tailwindcss/upgrade --force --config /home/flavorjones/code/oss/tailwindcss-rails/My\ Workspace/test-upgrade/config/tailwind.config.js from "." ≈ tailwindcss v4.1.5 │ Searching for CSS files in the current directory and its subdirectories… Error: Tailwind CSS is not installed at k.factory (file:///home/flavorjones/.local/share/mise/installs/node/22.12.0/lib/node_modules/@tailwindcss/upgrade/dist/index.mjs:194:727) at k.get (file:///home/flavorjones/.local/share/mise/installs/node/22.12.0/lib/node_modules/@tailwindcss/upgrade/dist/index.mjs:4:6572) at da (file:///home/flavorjones/.local/share/mise/installs/node/22.12.0/lib/node_modules/@tailwindcss/upgrade/dist/index.mjs:194:820) at E (file:///home/flavorjones/.local/share/mise/installs/node/22.12.0/lib/node_modules/@tailwindcss/upgrade/dist/index.mjs:194:641) at xl (file:///home/flavorjones/.local/share/mise/installs/node/22.12.0/lib/node_modules/@tailwindcss/upgrade/dist/index.mjs:241:10846) 

At some point we will probably need to unpin this at which point I am sincerely hoping that someone else will figure out how to do it.