Update contributing, deduplicate more functions

src/infra/wsl.ts

@@ -1,3 +1,4 @@
+import { readFileSync } from "node:fs";
 import fs from "node:fs/promises";
 
 let wslCached: boolean | null = null;
@@ -9,6 +10,40 @@ export function isWSLEnv(): boolean {
   return false;
 }
 
+/**
+ * Synchronously check if running in WSL.
+ * Checks env vars first, then /proc/version.
+ */
+export function isWSLSync(): boolean {
+  if (process.platform !== "linux") {
+    return false;
+  }
+  if (isWSLEnv()) {
+    return true;
+  }
+  try {
+    const release = readFileSync("/proc/version", "utf8").toLowerCase();
+    return release.includes("microsoft") || release.includes("wsl");
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Synchronously check if running in WSL2.
+ */
+export function isWSL2Sync(): boolean {
+  if (!isWSLSync()) {
+    return false;
+  }
+  try {
+    const version = readFileSync("/proc/version", "utf8").toLowerCase();
+    return version.includes("wsl2") || version.includes("microsoft-standard");
+  } catch {
+    return false;
+  }
+}
+
 export async function isWSL(): Promise<boolean> {
   if (wslCached !== null) {
     return wslCached;