fix(proxy): 去掉 poisoned-docs-path 里的死赋值初始值

Co-authored-by: github-code-quality[bot] <github-code-quality[bot]@users.noreply.github.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RtSNVtrEkCsFVHrbt4Zjgi

Author: 3 people

lib/poisoned-docs-path.ts

@@ -12,7 +12,7 @@
 export function isPoisonedDocsPath(pathname: string): boolean {
   const stripped = pathname.replace(/^\/(zh|en)(?=\/)/, "");
   if (!stripped.startsWith("/docs/")) return false;
-  let decoded = stripped;
+  let decoded: string;
   try {
     decoded = decodeURIComponent(stripped); // 防二次编码，对齐 redirectLeetcodeIfNeeded
   } catch {