feat: introduce MCP server, cross-platform runtime, and Showcase UI reorganization

- Showcase UI Reorganization:
  * Move web UI dashboard from root directory into apps/showcase_ui/ for cleaner project structure
  * Add 'artemis ui' CLI command (artemis/interfaces/cli/commands/ui.py) and launcher scripts for the interactive showcase console
- Standalone MCP Server & Notifiers (mcp_server/):
  * Implement dedicated MCP server package with mobile automation tools (device_state, inspect_trace, task_manager, task_runner)
  * Add multi-channel notifiers (AgentAPI, Desktop notifications, Webhooks, File output, and Composite routing)
  * Introduce background task runner and trace store for autonomous mobile execution monitoring
- Cross-Platform Runtime & Toolchain Support:
  * Add artemis/platform/ with OS-specific implementations for Linux, macOS (Darwin), and Windows
  * Add artemis/runtime/supervisor.py for resilient process and agent runtime supervision
  * Add artemis/toolchain/ with dependency resolution and SDK descriptors
  * Add cross-platform launcher scripts (start.sh, start.bat) and installer scripts (scripts/install_deps.*)
- Core Enhancements & Diagnostics:
  * Enhance coordinate normalization, OCR API fallback, and perception pipeline
  * Add credential validation (credentials_validator.py) and system diagnostics
  * Update bilingual documentation (README.md, README_CN.md) and architecture diagrams
- Test Suite Expansion:
  * Add integration tests for cloud gateway, remote ADB, and Artemis login
  * Add unit tests covering core diagnostics, platform detection, toolchain, credentials validator, optional OCR, and MCP tools

apps/showcase_ui/README.md

@@ -0,0 +1,31 @@
+# ✨ Artemis Showcase & User Workspace UI
+
+A modern, highly aesthetic presentation and interaction frontend built with **Angular 19** and **SCSS** for showcasing the Artemis mobile autonomous agent.
+
+## 🎨 Visual Design Highlights
+
+* **Aurora Glow Dynamics**: Ambient background lighting with smooth gradients.
+* **Glassmorphism Aesthetic**: Translucent frosted-glass panels with subtle borders.
+* **Real-time Dual-Pane Workspace**:
+  - **Left Pane (`app-agent-stream`)**: Live streaming of Agent thought steps, plan breakdowns, tool actions, and status.
+  - **Right Pane (`app-chat-interface`)**: Natural language chat input sidebar with interactive feedback and status pills.
+
+## 🚀 How to Run
+
+### Prerequisites
+- Node.js (>= 18)
+- Backend API running on `http://localhost:8000` (via `apps/admin_console` or `artemis ui`)
+
+### Development Server
+```bash
+cd apps/showcase_ui
+npm install
+npm start
+```
+This runs `ng serve --proxy-config proxy.conf.json` on **`http://localhost:4200/`**.
+
+### Production Build
+```bash
+npm run build
+```
+Build artifacts will be emitted to `dist/`, which can be served statically by `apps.admin_console` or `artemis ui`.