Update Textmate for types in a list and add unused keyword (#7535)

Setting "type" to bright red to make comparison obvious:
(screenshots taken from VSCode)
Before
<img width="446" height="150" alt="Screenshot 2026-07-20 135558"
src="https://github.com/user-attachments/assets/81249005-99f1-47bb-af4f-ad6e8f2404fb"
/>

After
<img width="429" height="149" alt="Screenshot 2026-07-20 135738"
src="https://github.com/user-attachments/assets/acc83086-fe19-4a18-a833-968daed56229"
/>

I'm not super familiar with textmate/highlightjs, but I think what was
happening on line 5 is that the "type" scope is being extended to the
`=` after `.y`.
Adding `,` as an "end" token fixes this, and I think this is what
highlightjs already does.

I've also added "unused" as a keyword.

utils/highlightjs/highlightjs_carbon_lang.js

@@ -72,6 +72,7 @@ export default function (hljs) {
       'then',
       'type',
       '_',
+      'unused',
       'var',
       'virtual',
       'where',

utils/textmate/Syntaxes/carbon.tmLanguage

@@ -607,7 +607,7 @@ THIS FILE IS AUTOGENERATED FROM carbon.tmLanguage.json. DO NOT EDIT.
 				</dict>
 				<dict>
 					<key>match</key>
-					<string>\b(and|as|generic|impls|in|like|not|or|partial|ref|runtime|template|where)\b</string>
+					<string>\b(and|as|generic|impls|in|like|not|or|partial|ref|runtime|template|unused|where)\b</string>
 					<key>name</key>
 					<string>keyword.control.carbon</string>
 				</dict>
@@ -801,7 +801,7 @@ THIS FILE IS AUTOGENERATED FROM carbon.tmLanguage.json. DO NOT EDIT.
 					<key>comment</key>
 					<string>Matches types in bindings.</string>
 					<key>end</key>
-					<string>(?=([;{=]|-&gt;|in|where))</string>
+					<string>(?=([;{=,]|-&gt;|in|where))</string>
 					<key>patterns</key>
 					<array>
 						<dict>

utils/vscode/carbon.tmLanguage.json

@@ -227,7 +227,7 @@
         {
           "comment": "Matches types in bindings.",
           "begin": ":",
-          "end": "(?=([;{=]|->|in|where))",
+          "end": "(?=([;{=,]|->|in|where))",
           "patterns": [
             { "include": "#common" },
             { "include": "#variables" },
@@ -346,7 +346,7 @@
         },
         {
           "name": "keyword.control.carbon",
-          "match": "\\b(and|as|generic|impls|in|like|not|or|partial|ref|runtime|template|where)\\b"
+          "match": "\\b(and|as|generic|impls|in|like|not|or|partial|ref|runtime|template|unused|where)\\b"
         }
       ]
     },