fix: add markResourceTiming polyfill to performance shim for Node.js v22 undici compatibility

Node.js v22 undici internal calls performance.markResourceTiming() after
every fetch. The performance shim was missing this method, causing
TypeError crashes in ACP mode when running with Node.js.

src/utils/performanceShim.ts

@@ -135,6 +135,9 @@ const shim = {
   clearResourceTimings: (() => {}) as typeof performance.clearResourceTimings,
   setResourceTimingBufferSize:
     (() => {}) as typeof performance.setResourceTimingBufferSize,
+  // Node.js v22 undici internal calls this after every fetch — must exist to
+  // avoid TypeError: markResourceTiming is not a function
+  markResourceTiming: (() => {}) as any,
   // Delegate read-only properties to the original
   get timeOrigin() {
     return original.timeOrigin
@@ -148,7 +151,7 @@ const shim = {
   toJSON() {
     return original.toJSON()
   },
-} as typeof performance
+} as unknown as typeof performance
 
 /**
  * Install the shim onto globalThis.performance. Safe to call multiple times.