fix: stabilize generated instructions README ordering (#1846)

Pass an explicit 'en' locale to localeCompare for instruction title
sorting in update-readme.mjs. Previously the default OS locale was
used, causing String.prototype.localeCompare to produce different
orderings on Windows vs Ubuntu (affecting characters like Korean and
Japanese CJK titles), which made the validate-readme CI workflow
non-deterministic.

Fixes the root cause of the locale-dependent sort instability.

eng/update-readme.mjs

@@ -303,7 +303,7 @@ function generateInstructionsSection(instructionsDir) {
   });
 
   // Sort by title alphabetically
-  instructionEntries.sort((a, b) => a.title.localeCompare(b.title));
+  instructionEntries.sort((a, b) => a.title.localeCompare(b.title, "en"));
 
   console.log(`Found ${instructionEntries.length} instruction files`);
 
@@ -673,7 +673,7 @@ function generateUnifiedModeSection(cfg) {
     return { file, filePath, title: extractTitle(filePath) };
   });
 
-  entries.sort((a, b) => a.title.localeCompare(b.title));
+  entries.sort((a, b) => a.title.localeCompare(b.title, "en"));
   console.log(
     `Unified mode generator: ${entries.length} files for extension ${extension}`
   );