Add a typed platform package to decouple the frontend from Tauri (#539)

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

packages/platform/src/registry.ts

@@ -0,0 +1,60 @@
+import type { Platform } from "./types";
+
+let installed: Platform | null = null;
+
+/**
+ * Install the host implementation. Called once at import time by this package's
+ * entry point, before any consumer's module body runs.
+ *
+ * It stays swappable at runtime because a browser build has to choose between
+ * talking to a local bridge and running in-page, and it can only find out which
+ * after it has tried to reach the bridge.
+ */
+export function setPlatform(next: Platform): void {
+  installed = next;
+}
+
+function host(): Platform {
+  if (installed == null) {
+    throw new Error("No platform installed. Import @yaakapp-internal/platform before using it.");
+  }
+  return installed;
+}
+
+/**
+ * The host, for everyone else to use.
+ *
+ * This is a fixed object that forwards to whatever is installed, so modules can
+ * import it at any time — including at module scope, which several boot-time
+ * modules do — without capturing a stale implementation.
+ *
+ * A host that has to connect before it can work (a WebSocket to the bridge)
+ * buffers inside its own `rpc`; nothing here waits on a connection, because the
+ * app's boot sequence calls commands while the module graph is still evaluating
+ * and cannot be made to wait.
+ */
+export const platform: Platform = {
+  get capabilities() {
+    return host().capabilities;
+  },
+  get window() {
+    return host().window;
+  },
+  get clipboard() {
+    return host().clipboard;
+  },
+  get dialog() {
+    return host().dialog;
+  },
+  get files() {
+    return host().files;
+  },
+  rpc: (cmd, payload) => host().rpc(cmd, payload),
+  rpcStream: (cmd, payload, onMessage) => host().rpcStream(cmd, payload, onMessage),
+  listen: (event, callback) => host().listen(event, callback),
+  emit: (event, payload) => host().emit(event, payload),
+  openUrl: (url) => host().openUrl(url),
+  revealItemInDir: (path) => host().revealItemInDir(path),
+  osType: () => host().osType(),
+  appIdentifier: () => host().appIdentifier(),
+};