feat(vats): boostrap-core connects vattp<->mailbox (WIP)

REGRESSION: bootstrap.js is skipped!

 - provide bootstrap() method per swingset
 - avoid: deliverInboundMessages before registerInboundHandler

 - refactor(vats): factor out connectVattpWithMailbox

packages/vats/decentral-config.json

@@ -44,7 +44,7 @@
       }
     },
     "bootstrap": {
-      "sourceSpec": "./src/bootstrap.js"
+      "sourceSpec": "./src/bootstrap-core.js"
     }
   }
 }

packages/vats/src/bootstrap-core.js

@@ -0,0 +1,43 @@
+// @ts-check
+import { E, Far } from '@agoric/far';
+
+/**
+ * @typedef { import('@agoric/eventual-send').EProxy } EProxy
+ * @typedef { ReturnType<typeof
+ *   import('@agoric/swingset-vat/src/devices/mailbox-src.js').buildRootDeviceNode> } MailboxDevice
+ * @typedef { ReturnType<typeof
+ *   import('@agoric/swingset-vat/src/vats/vat-tp.js').buildRootObject> } VattpVat
+ */
+
+/**
+ * Build root object of the bootstrap vat.
+ *
+ * @param {{
+ *   D: EProxy // approximately
+ * }} vatPowers
+ * @param {Record<string, unknown>} _vatParameters
+ */
+export function buildRootObject(vatPowers, _vatParameters) {
+  const { D } = vatPowers;
+
+  /**
+   * @param {VattpVat} vattp
+   * @param {MailboxDevice} mailbox
+   */
+  const connectVattpWithMailbox = async (vattp, mailbox) => {
+    D(mailbox).registerInboundHandler(vattp);
+    await E(vattp).registerMailboxDevice(mailbox);
+  };
+
+  return Far('bootstrap', {
+    /**
+     * Bootstrap vats and devices.
+     *
+     * @param {{vattp: VattpVat }} vats
+     * @param {{mailbox: MailboxDevice}} devices
+     */
+    bootstrap: async (vats, devices) => {
+      await connectVattpWithMailbox(vats.vattp, devices.mailbox);
+    },
+  });
+}