feat(cli): add remote build support for langgraph deploy (#7234)

**Description:** 

 - extend host_backend client with remote build support
- refactored `cli.py` for better clarity
- update tests

libs/cli/langgraph_cli/progress.py

@@ -18,6 +18,9 @@ class Progress:
         self._show_elapsed = elapsed
         # use this to make sure we don't kill thread when we set msg to ""
         self._stop = threading.Event()
+        # signalled when the spinner has no text on screen
+        self._line_clear = threading.Event()
+        self._line_clear.set()
         self.spinner_generator = self.spinning_cursor()
 
     def spinner_iteration(self):
@@ -43,13 +46,16 @@ class Progress:
         start = time.monotonic()
         while not self._stop.is_set():
             if not self.message:
+                self._line_clear.set()
                 time.sleep(self.delay)
                 continue
             if self._show_elapsed:
                 self.message = self._format_elapsed(time.monotonic() - start)
             message = self.message
             if not message:
+                self._line_clear.set()
                 continue
+            self._line_clear.clear()
             sys.stdout.write(next(self.spinner_generator) + " " + message)
             sys.stdout.flush()
             time.sleep(self.delay)
@@ -60,6 +66,7 @@ class Progress:
                 + "\b" * (len(message) + 2)
             )
             sys.stdout.flush()
+            self._line_clear.set()
 
     def __enter__(self) -> Callable[[str], None]:
         if sys.stdout.isatty():
@@ -69,6 +76,8 @@ class Progress:
             def set_message(message):
                 self.message = message
                 self._base_message = message or self._base_message
+                if not message:
+                    self._line_clear.wait(timeout=0.5)
 
             return set_message
         else: