fix: Resolve mypy type annotation errors

- Add proper type annotation for parser variable in parser_tool.py
- Fix store type annotation using lowercase dict instead of Dict
- Add null checks for self.last_input to prevent None attribute access
- Fix regex search with None argument by adding proper null check
- All 53 source files now pass mypy static analysis
- All 78 tests continue to pass

Author: vinod0m

src/agents/deepagent.py

@@ -90,7 +90,7 @@ def __init__(
         self.dry_run = bool(dry_run)
         self.llm: Any = None
         self.agent: Any = None
-        self.store = {}  # In-memory session store
+        self.store: dict[str, ChatMessageHistory] = {}  # In-memory session store
 
         if self.dry_run:
             self.tools = tools or [EchoTool()]
@@ -168,11 +168,11 @@ def invoke(self, input_data: dict, config: dict):
         self.last_input = input_data["input"]
 
         # Simple logic to simulate tool use for testing
-        if "parse" in self.last_input.lower():
+        if self.last_input and "parse" in self.last_input.lower():
             for tool in self.tools:
                 if tool.name == "DiagramParserTool":
                     # Extract file path from prompt (simple parsing)
-                    match = re.search(r"\'(.*?)\'", self.last_input)
+                    match = re.search(r"\'(.*?)\'", self.last_input) if self.last_input else None
                     if match:
                         file_path = match.group(1)
                         return {"output": tool._run(file_path)}

src/skills/parser_tool.py

@@ -25,6 +25,7 @@ def _run(self, file_path: str) -> str:
             # This is a simplified parser selection logic.
             # A more robust implementation would use a factory or
             # registration pattern.
+            parser: DrawIOParser | MermaidParser | PlantUMLParser
             if file_path.endswith((".drawio", ".xml")):
                 parser = DrawIOParser()
             elif file_path.endswith((".mmd", ".mermaid")):