[Feat] Custom MicroAgents. (#4983)

Co-authored-by: diwu-sf <di.wu@shadowfaxdata.com>

openhands/controller/agent.py

@@ -11,6 +11,7 @@ from openhands.core.exceptions import (
 )
 from openhands.llm.llm import LLM
 from openhands.runtime.plugins import PluginRequirement
+from openhands.utils.prompt import PromptManager
 
 
 class Agent(ABC):
@@ -33,6 +34,7 @@ class Agent(ABC):
         self.llm = llm
         self.config = config
         self._complete = False
+        self.prompt_manager: PromptManager | None = None
 
     @property
     def complete(self) -> bool: