feat: add multi-device concurrency, server lifecycle CLI, and unified execution stream

- Implement DevicePool and DeviceExecutionLock concurrency modes (per-device FIFO vs global serialization)
- Extend ArtemisClient SDK and CLI with explicit device targeting and concurrency strategy configuration
- Add server lifecycle management (artemis restart, stop, status) with cross-platform PID discovery
- Update MCP server tools to support multi-device dispatch, trace tagging, and per-device execution
- Enhance Showcase UI with step-by-step visual replay, playback speed controls, and device serial badges
- Add comprehensive unit test coverage and edge-case verification scripts

artemis/interfaces/sdk/task.py

@@ -44,9 +44,22 @@ class Task(BaseModel):
     goal: str = Field(..., description="High-level goal description")
     profile: Literal["flash", "pro"] = Field(default="pro", description="Execution profile")
     device_id: str = Field(default="default-device", description="Target device serial")
+    device_serial: str | None = Field(
+        default=None, description="Target device serial (alias for device_id)"
+    )
+    concurrency_mode: Literal["global", "per_device"] | None = Field(
+        default=None,
+        description="Concurrency mode: 'global' (1 across all devices) or 'per_device' (1 per device)",
+    )
     locked_package: str | None = Field(default=None, description="Package lock restriction")
     max_turns: int = Field(default=30, description="Turn cutoff limit")
 
+    def model_post_init(self, __context: Any) -> None:
+        if self.device_serial and self.device_id == "default-device":
+            self.device_id = self.device_serial
+        elif self.device_id != "default-device" and not self.device_serial:
+            self.device_serial = self.device_id
+
 
 class TaskResult(BaseModel):
     """Final structured outcome of a task execution."""
@@ -56,3 +69,4 @@ class TaskResult(BaseModel):
     turns: int
     output: Any = None
     error: str | None = None
+    device_id: str | None = None