feat: MCP tools integration for swarm agents

ToolExecutor:
- Persona-specific toolkit selection (forge gets code tools, echo gets search)
- Tool inference from task keywords (search→web_search, code→python)
- LLM-powered reasoning about tool selection
- Graceful degradation when Agno unavailable

PersonaNode Updates:
- Subscribe to swarm:events for task assignments
- Execute tasks using ToolExecutor when assigned
- Complete tasks via comms.complete_task()
- Track current_task for status monitoring

Tests:
- 19 new tests for tool execution
- All 6 personas covered
- Tool inference verification
- Edge cases (no toolkit, unknown tasks)

Total: 491 tests passing

src/swarm/persona_node.py

@@ -6,7 +6,8 @@ PersonaNode extends the base SwarmNode to:
    persona's preferred_keywords the node bids aggressively (bid_base ± jitter).
    Otherwise it bids at a higher, less-competitive rate.
 3. Register with the swarm registry under its persona's capabilities string.
-4. (Adaptive) Consult the swarm learner to adjust bids based on historical
+4. Execute tasks using persona-appropriate MCP tools when assigned.
+5. (Adaptive) Consult the swarm learner to adjust bids based on historical
    win/loss and success/failure data when available.
 
 Usage (via coordinator):
@@ -22,6 +23,7 @@ from typing import Optional
 from swarm.comms import SwarmComms, SwarmMessage
 from swarm.personas import PERSONAS, PersonaMeta
 from swarm.swarm_node import SwarmNode
+from swarm.tool_executor import ToolExecutor
 
 logger = logging.getLogger(__name__)
 
@@ -49,6 +51,27 @@ class PersonaNode(SwarmNode):
         self._meta = meta
         self._persona_id = persona_id
         self._use_learner = use_learner
+        
+        # Initialize tool executor for task execution
+        self._tool_executor: Optional[ToolExecutor] = None
+        try:
+            self._tool_executor = ToolExecutor.for_persona(
+                persona_id, agent_id
+            )
+        except Exception as exc:
+            logger.warning(
+                "Failed to initialize tools for %s: %s. "
+                "Agent will work in chat-only mode.",
+                agent_id, exc
+            )
+        
+        # Track current task
+        self._current_task: Optional[str] = None
+        
+        # Subscribe to task assignments
+        if self._comms:
+            self._comms.subscribe("swarm:events", self._on_swarm_event)
+        
         logger.debug("PersonaNode %s (%s) initialised", meta["name"], agent_id)
 
     # ── Bid strategy ─────────────────────────────────────────────────────────
@@ -102,6 +125,78 @@ class PersonaNode(SwarmNode):
             task_id,
             any(kw in description.lower() for kw in self._meta["preferred_keywords"]),
         )
+    
+    def _on_swarm_event(self, msg: SwarmMessage) -> None:
+        """Handle swarm events including task assignments."""
+        event_type = msg.data.get("type")
+        
+        if event_type == "task_assigned":
+            task_id = msg.data.get("task_id")
+            agent_id = msg.data.get("agent_id")
+            
+            # Check if assigned to us
+            if agent_id == self.agent_id:
+                self._handle_task_assignment(task_id)
+    
+    def _handle_task_assignment(self, task_id: str) -> None:
+        """Handle being assigned a task.
+        
+        This is where the agent actually does the work using its tools.
+        """
+        logger.info(
+            "PersonaNode %s assigned task %s, beginning execution",
+            self.name, task_id
+        )
+        self._current_task = task_id
+        
+        # Get task description from recent messages or lookup
+        # For now, we need to fetch the task details
+        try:
+            from swarm.tasks import get_task
+            task = get_task(task_id)
+            if not task:
+                logger.error("Task %s not found", task_id)
+                self._complete_task(task_id, "Error: Task not found")
+                return
+            
+            description = task.description
+            
+            # Execute using tools
+            if self._tool_executor:
+                result = self._tool_executor.execute_task(description)
+                
+                if result["success"]:
+                    output = result["result"]
+                    tools = ", ".join(result["tools_used"]) if result["tools_used"] else "none"
+                    completion_text = f"Task completed. Tools used: {tools}.\n\nResult:\n{output}"
+                else:
+                    completion_text = f"Task failed: {result.get('error', 'Unknown error')}"
+                
+                self._complete_task(task_id, completion_text)
+            else:
+                # No tools available - chat-only response
+                response = (
+                    f"I received task: {description}\n\n"
+                    f"However, I don't have access to specialized tools at the moment. "
+                    f"As a {self.name} specialist, I would typically use: "
+                    f"{self._meta['capabilities']}"
+                )
+                self._complete_task(task_id, response)
+                
+        except Exception as exc:
+            logger.exception("Task execution failed for %s", task_id)
+            self._complete_task(task_id, f"Error during execution: {exc}")
+        finally:
+            self._current_task = None
+    
+    def _complete_task(self, task_id: str, result: str) -> None:
+        """Mark task as complete and notify coordinator."""
+        if self._comms:
+            self._comms.complete_task(task_id, self.agent_id, result)
+        logger.info(
+            "PersonaNode %s completed task %s (result length: %d chars)",
+            self.name, task_id, len(result)
+        )
 
     # ── Properties ───────────────────────────────────────────────────────────
 
@@ -112,3 +207,15 @@ class PersonaNode(SwarmNode):
     @property
     def rate_sats(self) -> int:
         return self._meta["rate_sats"]
+    
+    @property
+    def current_task(self) -> Optional[str]:
+        """Return the task ID currently being executed, if any."""
+        return self._current_task
+    
+    @property
+    def tool_capabilities(self) -> list[str]:
+        """Return list of available tool names."""
+        if self._tool_executor:
+            return self._tool_executor.get_capabilities()
+        return []