Delete Tailwind's half and build the Workbench without it

Plan step 39 (parts 1-3, folded into one commit: PHP tests read the
deleted files directly, so they cannot land apart from it). Tailwind
leaves the whole stack:

- Delete resources/css/tailwind.css, tokens/theme.css and
  tokens/utilities.css. Neither token file declared an --md-sys-*
  custom property of its own (both only referenced tokens declared
  elsewhere), so nothing loses a value; the md-* interaction and text
  classes already mirror utilities.css's declarations exactly
  (foundation/interaction.css, text.css).
- npm uninstall tailwindcss @tailwindcss/vite; vite.config.js drops the
  plugin and its import; composer.json drops the tailwindcss keyword
  (no lock change — keywords are outside Composer's content hash).
- The Workbench now builds one CSS entry, workbench/resources/css/app.css
  (all.css, showcase.css and the scheme; package.css is folded in and
  removed) instead of two, used by ErrorPage::assets() and every
  browser-test probe page's raw @vite() call; the showcase's own pages
  still take their CSS from the bundle route.
- TokensTest and StylesheetsTest: the two facts theme.css and
  utilities.css carried (every scheme role becomes a colour, resolved
  on the element; md-type-* matches the type-* utilities) are asserted
  directly against the scheme and text.css now that there is no second
  copy to cross-check; StylesheetsTest gained a full-tree scan (every
  .css file under resources/css/ is reached from all.css or
  showcase.css, no exclusions left for Tailwind); the Workbench-entry
  test and every "moved out of tailwind.css" assertion updated for the
  single entry and its removal.
- DesignGuard.php's comments and the development skill's setup section
  no longer name the deleted files or a second Tailwind entry.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

package.json

@@ -13,12 +13,10 @@
     },
     "devDependencies": {
         "@material/material-color-utilities": "^0.4.0",
-        "@tailwindcss/vite": "^4.3.3",
         "esbuild": "^0.28.2",
         "fontkit": "^2.0.4",
         "laravel-vite-plugin": "^3.2.0",
         "playwright": "^1.62.1",
-        "tailwindcss": "^4.3.3",
         "vite": "^8.2.2"
     }
 }