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

apps/showcase_ui/src/app/components/agent-stream/agent-stream.component.html

@@ -68,6 +68,11 @@
             {{ getTaskStatus(session) | uppercase }}
           </span>
           <div class="item-header-actions">
+            <span class="item-device" *ngIf="getDeviceSerial(session)" [title]="'Device: ' + getDeviceSerial(session)">
+              <span class="material-symbols-outlined device-icon">phone_android</span>
+              <span class="device-name">{{ getDeviceSerial(session) }}</span>
+            </span>
+            <span class="item-time-divider" *ngIf="getDeviceSerial(session)">·</span>
             <span class="item-time">{{ session.start_time * 1000 | date:'shortTime' }}</span>
             <button
               *ngIf="getTaskStatus(session) !== 'running' && getTaskStatus(session) !== 'paused'"
@@ -113,6 +118,11 @@
               {{ getTaskStatus(session) | uppercase }}
             </span>
             <div class="item-header-actions">
+              <span class="item-device" *ngIf="getDeviceSerial(session)" [title]="'Device: ' + getDeviceSerial(session)">
+                <span class="material-symbols-outlined device-icon">phone_android</span>
+                <span class="device-name">{{ getDeviceSerial(session) }}</span>
+              </span>
+              <span class="item-time-divider" *ngIf="getDeviceSerial(session)">·</span>
               <span class="item-time">{{ session.start_time * 1000 | date:'shortTime' }}</span>
             <button
               *ngIf="getTaskStatus(session) !== 'running' && getTaskStatus(session) !== 'paused'"