feat: add await syntax for direct async function calls and new generator/phonebook apps

Add compiler support for calling async functions directly with `await fn(args)` syntax, automatically translating to `await fn.call(args)`. Introduce `create_merge` Makefile target for merging Wren source files. Include new `apps/generator.wren` source code generator using OpenRouter API, `apps/phonebook.wren` CLI phonebook with SQLite backend, and `apps/minitut.md` Wren tutorial reference. Update `example/await_demo.wren` with parameterized async functions, nested awaits, and expression usage. Fix JSON parsing in `example/openrouter_demo.wren` to strip markdown code fences. Document new await syntax in `manual/api/scheduler.html`.

apps/phonebook.wren

@@ -0,0 +1,97 @@
+// wren source code generator v1.0
+// Generation time: 0.101419
+
+import "io" for File, Directory, Stdin, Stdout
+import "sqlite" for Database
+
+class Phonebook {
+  construct new() {
+    _db = Database.memory()
+    init_()
+  }
+
+  init_() {
+    _db.execute("CREATE TABLE IF NOT EXISTS contacts (id INTEGER PRIMARY KEY, name TEXT, phone TEXT)", [])
+  }
+
+  add(name, phone) {
+    _db.execute("INSERT INTO contacts (name, phone) VALUES (?, ?)", [name, phone])
+    System.print("Contact added: %(name)")
+  }
+
+  list() {
+    var rows = _db.query("SELECT * FROM contacts", [])
+    if (rows.isEmpty) {
+      System.print("No contacts found.")
+      return
+    }
+    System.print("\n--- Phonebook ---")
+    for (row in rows) {
+      System.print("%(row["name"]) : %(row["phone"])")
+    }
+    System.print("")
+  }
+
+  search(name) {
+    var rows = _db.query("SELECT * FROM contacts WHERE name LIKE ?", ["\%" + name + "\%"])
+    if (rows.isEmpty) {
+      System.print("No contacts found for '%(name)'.")
+      return
+    }
+    System.print("\n--- Search Results ---")
+    for (row in rows) {
+      System.print("%(row[1]) : %(row[2])")
+    }
+    System.print("")
+  }
+
+  delete(name) {
+    _db.execute("DELETE FROM contacts WHERE name = ?", [name])
+    System.print("Contact deleted: %(name)")
+  }
+
+  run() {
+    System.print("\n=== CLI Phonebook ===")
+    var running = true
+    while (running) {
+      System.print("\n1. Add contact")
+      System.print("2. List contacts")
+      System.print("3. Search contact")
+      System.print("4. Delete contact")
+      System.print("5. Exit")
+      System.write("Choose option: ")
+      Stdout.flush()
+      var choice = Stdin.readLine().trim()
+
+      if (choice == "1") {
+        System.write("Name: ")
+        Stdout.flush()
+        var name = Stdin.readLine().trim()
+        System.write("Phone: ")
+        Stdout.flush()
+        var phone = Stdin.readLine().trim()
+        add(name, phone)
+      } else if (choice == "2") {
+        list()
+      } else if (choice == "3") {
+        System.write("Search name: ")
+        Stdout.flush()
+        var name = Stdin.readLine().trim()
+        search(name)
+      } else if (choice == "4") {
+        System.write("Contact name to delete: ")
+        Stdout.flush()
+        var name = Stdin.readLine().trim()
+        delete(name)
+      } else if (choice == "5") {
+        System.print("Goodbye!")
+        running = false
+      } else {
+        System.print("Invalid option.")
+      }
+    }
+  }
+}
+
+var pb = Phonebook.new()
+pb.run()