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/desktop.py

@@ -0,0 +1,92 @@
+# 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.
+
+"""Desktop Toast / OS notification adapter."""
+
+import logging
+import os
+import shutil
+import subprocess
+import sys
+from typing import Any
+
+from mcp_server.notifiers.base import BaseNotifier
+
+logger = logging.getLogger("mcp_server.notifiers.desktop")
+
+
+class DesktopNotifier(BaseNotifier):
+    """Notifier that displays native desktop notifications when explicitly enabled."""
+
+    @property
+    def name(self) -> str:
+        return "desktop"
+
+    def is_available(self) -> bool:
+        return os.getenv("ARTEMIS_DESKTOP_NOTIFY", "").lower() in ("1", "true", "yes")
+
+    def notify(
+        self,
+        conversation_id: str,
+        message: str,
+        title: str | None = None,
+        event_type: str = "completed",
+        payload: dict[str, Any] | None = None,
+    ) -> bool:
+        if not self.is_available():
+            return False
+
+        header = title or f"☕ Artemis Task {event_type.capitalize()}"
+        clean_body = message.split("\n\n")[0][:120]
+
+        try:
+            if sys.platform == "linux":
+                if shutil.which("notify-send"):
+                    subprocess.run(
+                        ["notify-send", header, clean_body],
+                        stdout=subprocess.DEVNULL,
+                        stderr=subprocess.DEVNULL,
+                        timeout=3,
+                    )
+                    return True
+            elif sys.platform == "darwin":
+                if shutil.which("osascript"):
+                    script = f'display notification "{clean_body}" with title "{header}"'
+                    subprocess.run(
+                        ["osascript", "-e", script],
+                        stdout=subprocess.DEVNULL,
+                        stderr=subprocess.DEVNULL,
+                        timeout=3,
+                    )
+                    return True
+            elif sys.platform == "win32":
+                ps_cmd = (
+                    f"[Windows.UI.Notifications.ToastNotificationManager, Windows.UI.Notifications, ContentType = WindowsRuntime] > $null; "
+                    f"$template = [Windows.UI.Notifications.ToastNotificationManager]::GetTemplateContent([Windows.UI.Notifications.ToastTemplateType]::ToastText02); "
+                    f'$textNodes = $template.GetElementsByTagName("text"); '
+                    f'$textNodes.Item(0).AppendChild($template.CreateTextNode("{header}")) > $null; '
+                    f'$textNodes.Item(1).AppendChild($template.CreateTextNode("{clean_body}")) > $null; '
+                    f"$toast = [Windows.UI.Notifications.ToastNotification]::new($template); "
+                    f'[Windows.UI.Notifications.ToastNotificationManager]::CreateToastNotifier("Artemis").Show($toast);'
+                )
+                subprocess.run(
+                    ["powershell", "-NoProfile", "-Command", ps_cmd],
+                    stdout=subprocess.DEVNULL,
+                    stderr=subprocess.DEVNULL,
+                    timeout=5,
+                )
+                return True
+        except Exception as e:
+            logger.debug(f"Desktop notification failed: {e}")
+        return False