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/tools/mobile/ocr.py

@@ -30,7 +30,7 @@ from artemis.graph.state import State
 from artemis.tools.base import ArtemisTool, ToolCategory, ToolRegistry
 from artemis.tools.tool_wrapper import ToolWrapper
 from artemis.utils.logger import get_logger
-from artemis.utils.ocr_api import perform_ocr
+from artemis.utils.ocr_api import is_ocr_configured, perform_ocr
 
 
 class OcrArgs(BaseModel):
@@ -144,6 +144,9 @@ class OcrRecognitionTool(ArtemisTool):
             category=category,
         )
 
+    def is_available(self, ctx: Any = None) -> bool:
+        return is_ocr_configured()
+
     # pylint: disable=too-many-arguments,too-many-positional-arguments
     async def execute(
         self,
@@ -207,4 +210,5 @@ ocr_recognition_wrapper = ToolWrapper(
     tool_fn_getter=get_ocr_tool,
     on_success_fn=lambda output: f"OCR Recognition successful. Results:\n{output}",
     on_failure_fn=lambda error: f"OCR Recognition failed: {error}",
+    is_available_fn=lambda ctx: is_ocr_configured(),
 )