fix(cli): Apply pyink formatting to agent_loader.py

Reformatted code to comply with pyink style guide:
- Line length limits enforced
- Multi-line conditional formatting improved
- String concatenation formatting optimized

Addresses lint check failure in PR google#3196.

Author: pantsjj

src/google/adk/cli/utils/agent_loader.py

@@ -227,30 +227,27 @@ def _perform_load(self, agent_name: str) -> Union[BaseAgent, App]:
     # Check if user might be in the wrong directory
     hint = ""
     agents_path = Path(agents_dir)
-    if agents_path.joinpath("agent.py").is_file() or agents_path.joinpath(
-        "root_agent.yaml"
-    ).is_file():
+    if (
+        agents_path.joinpath("agent.py").is_file()
+        or agents_path.joinpath("root_agent.yaml").is_file()
+    ):
       hint = (
-          "\n\nHINT: It looks like you might be running 'adk web' from inside an"
-          " agent directory. Try running 'adk web .' from the parent directory"
-          " that contains your agent folder, not from within the agent folder"
-          " itself."
+          "\n\nHINT: It looks like you might be running 'adk web' from inside"
+          " an agent directory. Try running 'adk web .' from the parent"
+          " directory that contains your agent folder, not from within the"
+          " agent folder itself."
       )
 
     raise ValueError(
         f"No root_agent found for '{agent_name}'. Searched in"
         f" '{actual_agent_name}.agent.root_agent',"
         f" '{actual_agent_name}.root_agent' and"
-        f" '{actual_agent_name}/root_agent.yaml'."
-        f"\n\nExpected directory structure:"
-        f"\n  <agents_dir>/"
-        f"\n    {actual_agent_name}/"
-        f"\n      agent.py (with root_agent) OR"
-        f"\n      root_agent.yaml"
-        f"\n\nThen run: adk web <agents_dir>"
-        f"\n\nEnsure '{agents_dir}/{actual_agent_name}' is structured correctly,"
-        " an .env file can be loaded if present, and a root_agent is exposed."
-        f"{hint}"
+        f" '{actual_agent_name}/root_agent.yaml'.\n\nExpected directory"
+        f" structure:\n  <agents_dir>/\n    {actual_agent_name}/\n     "
+        " agent.py (with root_agent) OR\n      root_agent.yaml\n\nThen run:"
+        f" adk web <agents_dir>\n\nEnsure '{agents_dir}/{actual_agent_name}' is"
+        " structured correctly, an .env file can be loaded if present, and a"
+        f" root_agent is exposed.{hint}"
     )
 
   def _ensure_app_name_matches(