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

mcp_server/notifiers/__init__.py

@@ -0,0 +1,66 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Universal MCP Multi-Environment Notification System."""
+
+from typing import Any, Dict, Optional
+
+from mcp_server.notifiers.agentapi import AgentApiNotifier
+from mcp_server.notifiers.base import BaseNotifier
+from mcp_server.notifiers.composite import CompositeNotifier
+from mcp_server.notifiers.desktop import DesktopNotifier
+from mcp_server.notifiers.file import FileNotifier
+from mcp_server.notifiers.webhook import WebhookNotifier
+
+_default_notifier = CompositeNotifier()
+
+
+def get_default_notifier() -> CompositeNotifier:
+    """Returns the global default composite notifier instance."""
+    return _default_notifier
+
+
+def notify(
+    conversation_id: str,
+    message: str,
+    title: str | None = None,
+    event_type: str = "completed",
+    payload: dict[str, Any] | None = None,
+) -> bool:
+    """Dispatches a notification across all available channels (AgentAPI, Webhook, Desktop, File)."""
+    return _default_notifier.notify(
+        conversation_id=conversation_id,
+        message=message,
+        title=title,
+        event_type=event_type,
+        payload=payload,
+    )
+
+
+def notify_jetski(conversation_id: str, message: str) -> bool:
+    """Backward-compatible alias for notify()."""
+    return notify(conversation_id=conversation_id, message=message, event_type="completed")
+
+
+__all__ = [
+    "BaseNotifier",
+    "AgentApiNotifier",
+    "WebhookNotifier",
+    "DesktopNotifier",
+    "FileNotifier",
+    "CompositeNotifier",
+    "get_default_notifier",
+    "notify",
+    "notify_jetski",
+]