fix(no-unlocalized-strings): ignore directive prologues

Ignore JavaScript/React directive prologues like "use strict",
"use client", and "use server" which were incorrectly flagged
as unlocalized strings because they contain letters and spaces.

Author: swernerx

src/rules/no-unlocalized-strings.test.ts

@@ -393,6 +393,13 @@ ruleTester.run("no-unlocalized-strings", noUnlocalizedStrings, {
     { code: 'import name from "hello"', filename: "test.tsx" },
     { code: 'export * from "hello_export_all"', filename: "test.tsx" },
 
+    // JavaScript/React directive prologues
+    { code: '"use strict"', filename: "test.tsx" },
+    { code: '"use client"', filename: "test.tsx" },
+    { code: '"use server"', filename: "test.tsx" },
+    { code: '"use client"\nimport React from "react"', filename: "test.tsx" },
+    { code: '"use server"\nexport async function action() {}', filename: "test.tsx" },
+
     // =========================================================================
     // Branded types with __linguiIgnore
     // =========================================================================

src/rules/no-unlocalized-strings.ts

@@ -853,6 +853,37 @@ function isInsideStylingConstant(node: TSESTree.Node): boolean {
 // Syntax Context Checks (non-user-facing locations)
 // ============================================================================
 
+/** Known JavaScript/React directive prologues */
+const DIRECTIVE_PROLOGUES = new Set(["use strict", "use client", "use server"])
+
+/**
+ * Checks if a string literal is a JavaScript directive prologue.
+ *
+ * Directive prologues are special string literals at the start of a script/module:
+ * - "use strict" - JavaScript strict mode
+ * - "use client" - React Server Components client boundary
+ * - "use server" - React Server Components server actions
+ */
+function isDirectivePrologue(node: TSESTree.Node): boolean {
+  if (node.type !== AST_NODE_TYPES.Literal || typeof node.value !== "string") {
+    return false
+  }
+
+  // Check if this is a known directive
+  if (!DIRECTIVE_PROLOGUES.has(node.value)) {
+    return false
+  }
+
+  // Directive prologues must be expression statements at the program level
+  const parent = node.parent
+  if (parent.type !== AST_NODE_TYPES.ExpressionStatement) {
+    return false
+  }
+
+  const grandparent = parent.parent
+  return grandparent.type === AST_NODE_TYPES.Program
+}
+
 /**
  * Checks if a string is in a TypeScript type context (not runtime code).
  *
@@ -1356,6 +1387,11 @@ export const noUnlocalizedStrings = createRule<[Options], MessageId>({
         return
       }
 
+      // JavaScript/React directive prologues: "use strict", "use client", "use server"
+      if (isDirectivePrologue(node)) {
+        return
+      }
+
       // TypeScript type definition (not runtime)
       if (isInTypeContext(node)) {
         return