Move tailwind off the deprecated module.register() (closes #32)

Every frontend build printed Node's DEP0205 warning. The trace names
@tailwindcss/node, which @tailwindcss/vite brings in at its own exact
version; tailwind 4.3.1 calls module.registerHooks() where Node has it.
@tailwindcss/vite and tailwindcss move to 4.3.3, inside the ranges
package.json already allows, so only yarn.lock changes, every entry
still with an integrity hash. tailwindcss moves too so that one tailwind
version is installed.

Model: opus-5-5

TODO.md

@@ -23,6 +23,17 @@ latest run passes.
 
 # Completed Steps
 
+- 2026-10-04: the frontend build no longer prints Node's warning that
+  `module.register()` is deprecated (issue #32). The call was in
+  `@tailwindcss/node`, which `@tailwindcss/vite` brings in at its own exact
+  version; tailwind 4.3.1 calls `module.registerHooks()` instead where Node has
+  it. `yarn.lock` now has `@tailwindcss/vite` and `tailwindcss` at 4.3.3, inside
+  the ranges `package.json` already allowed, and tailwind's own dependencies
+  moved with them. The built CSS changes only in how it is written out, in
+  tailwind's Firefox focus-ring rule, which no longer applies to iframes (the
+  page has none, so nothing on it looks different), and in tailwind's default
+  sans-serif font list, which the page does not use: `body` sets a monospace
+  font
 - 2026-10-03: the frontend has a real linter (issue #47, and item 2 of issue
   #28): `eslint` with its recommended rules, set in `eslint.config.js`, runs in
   a new `frontend-lint` stage of `Dockerfile`, which the frontend stage waits