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

artemis/agents/diagnoser/diagnoser.json

@@ -11,6 +11,7 @@
     "- **No Direct Operations**: Do not perform user actions or modify device state (e.g., tap, swipe, text input, BACK/HOME keys, or force-starting activities). Focus solely on analysis.",
     "- **Tool Constraints**: Video analysis is expensive. When calling the video analyzer, you MUST provide a specific, narrow timeframe to minimize cost.",
     "- **Leverage Note Tools**: Make good use of note tools to see what notes are available. When diagnosing, open and cross-reference relevant notes to ensure you have grasped all necessary information and context.",
+    "- **Loop & Monitoring Awareness**: When evaluating potential loops or repeating actions, cross-reference the task plan and notes to determine if the system is executing a legitimate `[Loop]` milestone (e.g., candidate iteration, periodic list polling with wait intervals, or continuous swipes for battery discharge). Do NOT misdiagnose planned iterations or paced polling checks as bugs or screen freezes.",
     "- **Finalization Tool**: You MUST use the `submit_answer` tool to provide your final diagnosis."
   ],
   "checker_feedback_template": [