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`.

example/openrouter_demo.wren

@@ -39,7 +39,15 @@ System.print("Status: %(response.statusCode)")
 System.print("")
 
 if (response.ok) {
-  var data = Json.parse(response.body)
+  let text  = response.body
+      if(text.startsWith("```")){
+        text = text.trim("```")
+        text = text.trim("json")
+        text = text.trim("\n")
+
+      }
+    System.print(text)
+  var data = Json.parse(text)
   if (data != null && data["choices"] != null && data["choices"].count > 0) {
     var message = data["choices"][0]["message"]
     if (message != null && message["content"] != null) {