fix(infra): make browser relay bind address configurable

Add browser.relayBindHost config option so the Chrome extension relay
server can bind to a non-loopback address (e.g. 0.0.0.0 for WSL2).
Defaults to 127.0.0.1 when unset, preserving current behavior.

Closes #39214

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/browser/server-context.availability.ts

@@ -117,7 +117,10 @@ export function createProfileAvailability({
 
     if (isExtension) {
       if (!httpReachable) {
-        await ensureChromeExtensionRelayServer({ cdpUrl: profile.cdpUrl });
+        await ensureChromeExtensionRelayServer({
+          cdpUrl: profile.cdpUrl,
+          bindHost: current.resolved.relayBindHost,
+        });
         if (!(await isHttpReachable(PROFILE_ATTACH_RETRY_TIMEOUT_MS))) {
           throw new Error(
             `Chrome extension relay for profile "${profile.name}" is not reachable at ${profile.cdpUrl}.`,