Add VS Code CSS validation support (#5893)

## Summary

Adds VS Code custom CSS data for proper validation of non-standard CSS
properties and Tailwind v4 directives.

## Changes

- **What**: Custom CSS data files for VS Code CSS language service
validation
  - `app-region` - Electron draggable regions  
  - `speak` - Deprecated aural stylesheet property
  - `@custom-variant` - Tailwind v4 custom variant definitions
  - `@utility` - Tailwind v4 custom utility definitions
- Fixes broken documentation links in existing Tailwind directive
references

## Review Focus

Documentation links verified against current Tailwind CSS and Electron
documentation.

## Screenshots

Current: Yellow squigglies

<img width="338" height="179" alt="image"
src="https://github.com/user-attachments/assets/652040f5-8e0b-486b-95f6-2fa8f9bf9ba7"
/><img width="499" height="180" alt="image"
src="https://github.com/user-attachments/assets/43d16210-7fbf-4ef8-b0e1-9a16e59d1d85"
/>

Proposed: Satisfying lack of warnings

<img width="173" height="62" alt="image"
src="https://github.com/user-attachments/assets/25f1c1c4-22b7-483b-9848-3030a3c0dc86"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5893-Add-VS-Code-CSS-validation-support-2806d73d3650813fb5f1e176360c5b7e)
by [Unito](https://www.unito.io)

---------

Consequences of `@apply` usage may include but are not limited to:
- A strong talking-to
- Receipt of a corrective directive missive
- Upsetting @DrJKL

Co-authored-by: Alexander Brown <drjkl@comfy.org>

.gitignore

@@ -31,6 +31,7 @@ CLAUDE.local.md
 *.code-workspace
 !.vscode/extensions.json
 !.vscode/tailwind.json
+!.vscode/custom-css.json
 !.vscode/settings.json.default
 !.vscode/launch.json.default
 .idea

.vscode/custom-css.json

@@ -0,0 +1,50 @@
+{
+  "version": 1.1,
+  "properties": [
+    {
+      "name": "app-region",
+      "description": "Electron-specific CSS property that defines draggable regions in custom title bar windows. Setting 'drag' marks a rectangular area as draggable for moving the window; 'no-drag' excludes areas from the draggable region.",
+      "values": [
+        {
+          "name": "drag",
+          "description": "Marks the element as draggable for moving the Electron window"
+        },
+        {
+          "name": "no-drag",
+          "description": "Excludes the element from being used to drag the Electron window"
+        }
+      ],
+      "references": [
+        {
+          "name": "Electron Window Customization",
+          "url": "https://www.electronjs.org/docs/latest/tutorial/window-customization"
+        }
+      ]
+    },
+    {
+      "name": "speak",
+      "description": "Deprecated CSS2 aural stylesheet property for controlling screen reader speech. Use ARIA attributes instead.",
+      "values": [
+        {
+          "name": "auto",
+          "description": "Content is read aurally if element is not a block and is visible"
+        },
+        {
+          "name": "never",
+          "description": "Content will not be read aurally"
+        },
+        {
+          "name": "always",
+          "description": "Content will be read aurally regardless of display settings"
+        }
+      ],
+      "references": [
+        {
+          "name": "CSS-Tricks Reference",
+          "url": "https://css-tricks.com/almanac/properties/s/speak/"
+        }
+      ],
+      "status": "obsolete"
+    }
+  ]
+}

.vscode/settings.json.default

@@ -1,5 +1,6 @@
 {
   "css.customData": [
-    ".vscode/tailwind.json"
+    ".vscode/tailwind.json",
+    ".vscode/custom-css.json"
   ]
 }

.vscode/tailwind.json

@@ -7,7 +7,7 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#import"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#import-directive"
         }
       ]
     },
@@ -17,7 +17,7 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#theme"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#theme-directive"
         }
       ]
     },
@@ -27,17 +27,17 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#layer"
+          "url": "https://tailwindcss.com/docs/theme#layers"
         }
       ]
     },
     {
       "name": "@apply",
-      "description": "Use the `@apply` directive to inline any existing utility classes into your own custom CSS. This is useful when you find a common utility pattern in your HTML that you’d like to extract to a new component.",
+      "description": "DO NOT USE. IF YOU ARE CAUGHT USING @apply YOU WILL FACE SEVERE CONSEQUENCES.",
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#apply"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#apply-directive"
         }
       ]
     },
@@ -47,7 +47,7 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#config"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#config-directive"
         }
       ]
     },
@@ -57,7 +57,7 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#reference"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#reference-directive"
         }
       ]
     },
@@ -67,7 +67,27 @@
       "references": [
         {
           "name": "Tailwind Documentation",
-          "url": "https://tailwindcss.com/docs/functions-and-directives#plugin"
+          "url": "https://tailwindcss.com/docs/functions-and-directives#plugin-directive"
+        }
+      ]
+    },
+    {
+      "name": "@custom-variant",
+      "description": "Use the `@custom-variant` directive to add a custom variant to your project. Custom variants can be used with utilities like `hover`, `focus`, and responsive breakpoints. Use `@slot` inside the variant to indicate where the utility's styles should be inserted.",
+      "references": [
+        {
+          "name": "Tailwind Documentation",
+          "url": "https://tailwindcss.com/docs/adding-custom-styles#adding-custom-variants"
+        }
+      ]
+    },
+    {
+      "name": "@utility",
+      "description": "Use the `@utility` directive to add custom utilities to your project. Custom utilities work with all variants like `hover`, `focus`, and responsive variants. Use `--value()` to create functional utilities that accept arguments.",
+      "references": [
+        {
+          "name": "Tailwind Documentation",
+          "url": "https://tailwindcss.com/docs/adding-custom-styles#adding-custom-utilities"
         }
       ]
     }