feat(app): export isDev platform flag and enable runtime metrics in dev

Adds a shared isDev constant alongside isWeb/isNative and wires daemon
clients to collect runtime metrics (10s interval) only in development.

packages/app/src/utils/scroll-jank-investigation.ts

@@ -1,4 +1,4 @@
-import { isWeb } from "@/constants/platform";
+import { isDev, isWeb } from "@/constants/platform";
 
 type ListenerStats = {
   adds: number;
@@ -91,7 +91,6 @@ const SOURCE_LABEL = "[ScrollJankInvestigation]";
 
 function shouldInstall(): boolean {
   const runtime = globalThis as ScrollInvestigationGlobal;
-  const isDev = Boolean((globalThis as { __DEV__?: boolean }).__DEV__);
   return isWeb && isDev && !runtime.__PASEO_SCROLL_JANK_INVESTIGATION_DISABLED__;
 }