fix: register text as a supported language

src/Highlighter.php

@@ -84,6 +84,7 @@ public function __construct(
             ->addLanguage(new ScssLanguage())
             ->addLanguage(new SqlLanguage())
             ->addLanguage(new TerminalLanguage())
+            ->addLanguage(new TextLanguage())
             ->addLanguage(new TerraformLanguage())
             ->addLanguage(new TypeScriptLanguage())
             ->addLanguage(new XmlLanguage())

tests/Bench/Fixtures/text.txt

@@ -0,0 +1,3 @@
+Plain text may contain protocol method names such as resources/list and mcp:list.
+It may also contain HTTP header names such as Sec-Fetch-Site.
+No syntax highlighting should be applied to this content.

tests/Bench/HighlighterBench.php

@@ -42,6 +42,7 @@ final class HighlighterBench
         'terminal' => 'terminal.txt',
         'terraform' => 'terraform.txt',
         'typescript' => 'typescript.txt',
+        'txt' => 'text.txt',
         'twig' => 'twig.txt',
         'vue' => 'vue.txt',
         'xml' => 'xml.txt',

tests/HighlighterTest.php

@@ -151,4 +151,14 @@ public function test_fallback_language(): void
             $highlighted,
         );
     }
+
+    #[Test]
+    public function text_language_does_not_use_the_configured_fallback_language(): void
+    {
+        $highlighter = new Highlighter(fallbackLanguage: new PhpLanguage());
+
+        $this->assertSame('mcp:list', $highlighter->parse('mcp:list', 'txt'));
+        $this->assertSame('resources/list', $highlighter->parse('resources/list', 'text'));
+        $this->assertSame('Sec-Fetch-Site', $highlighter->parse('Sec-Fetch-Site', 'txt'));
+    }
 }