refactor: simplify loadCustomStrings function signature and error handling

Make customStringsArg parameter required since caller already checks existence. Remove redundant try-catch block in main.ts to avoid duplicate error logging since loadCustomStrings already provides descriptive error messages.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: strickvl

src/node/i18n/index.ts

@@ -25,10 +25,7 @@ const defaultResources = {
 }
 
 
-export async function loadCustomStrings(customStringsArg?: string): Promise<void> {
-  if (!customStringsArg) {
-    return
-  }
+export async function loadCustomStrings(customStringsArg: string): Promise<void> {
 
   try {
     let customStringsData: Record<string, any>

src/node/main.ts

@@ -125,13 +125,8 @@ export const runCodeServer = async (
 
   // Load custom strings if provided
   if (args["custom-strings"]) {
-    try {
-      await loadCustomStrings(args["custom-strings"])
-      logger.info("Loaded custom strings")
-    } catch (error) {
-      logger.error("Failed to load custom strings", field("error", error))
-      throw error
-    }
+    await loadCustomStrings(args["custom-strings"])
+    logger.info("Loaded custom strings")
   }
 
   logger.info(`Using user-data-dir ${args["user-data-dir"]}`)