Add the Yaak Bridge so a browser tab can run the real engine

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/platform/src/index.ts

@@ -1,14 +1,30 @@
+import { createBridgePlatform } from "./bridge";
+import { bridgeConfig, promptForToken, shouldUseBridge } from "./connect";
 import { setPlatform } from "./registry";
 import { createTauriPlatform } from "./tauri";
 
-// Desktop is the only host today, so it is installed unconditionally and
-// synchronously — several modules call commands while the module graph is still
-// evaluating, so there is no later moment to do this in.
+// This line is the swap point, and it has to run synchronously: several modules
+// call commands while the module graph is still evaluating, so there is no
+// later moment to install a host in.
 //
-// This line is the swap point. A browser build selects its own host here, and
-// because nothing else in the app imports a host directly, that is the whole
-// change.
-setPlatform(createTauriPlatform());
+// Both hosts are constructible without waiting for anything. The bridge host
+// opens its connection in the background and queues calls made before it lands,
+// which is why picking a host here does not mean blocking on one.
+if (shouldUseBridge()) {
+  const config = bridgeConfig();
+  if (config == null) {
+    // No token yet: put the connect form on screen and install a host that
+    // never connects. Boot then stalls at its own top-level await rather than
+    // failing somewhere that doesn't explain itself — and it stalls in the one
+    // place already designed to wait, which keeps this file synchronous.
+    promptForToken();
+    setPlatform(createBridgePlatform(window.location.origin, null));
+  } else {
+    setPlatform(createBridgePlatform(config.url, config.token));
+  }
+} else {
+  setPlatform(createTauriPlatform());
+}
 
 export * from "./capabilities";
 export { platform, setPlatform } from "./registry";