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

tests/unit/agents/test_plan_mutation_guardrails.py

@@ -0,0 +1,87 @@
+# 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.
+
+from unittest.mock import MagicMock
+from artemis.graph.graph import check_plan_mutation_rejections
+from artemis.graph.state import State
+
+
+def test_check_plan_mutation_incomplete_nested():
+    content_before = "- [/] Main task\n  - [ ] Subtask 1"
+    content_after = "- [x] Main task\n  - [ ] Subtask 1"
+    res = check_plan_mutation_rejections(content_before, content_after)
+    assert res is not None
+    assert "goals in the task plan that have not been marked as completed" in res
+
+
+def test_check_plan_mutation_delete_continuous_loop():
+    content_before = (
+        "- [x] Open app\n"
+        "- [/] [Loop] Periodically monitor for new emails "
+        "(Exit: Continuous monitoring until manually stopped; Interval: every 5 minutes)\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    content_after = (
+        "- [x] Open app\n"
+        "- [x] Monitor for new emails\n"
+        "  - [x] Baseline established\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    res = check_plan_mutation_rejections(content_before, content_after)
+    assert res is not None
+    assert "cannot delete an active [Loop]" in res
+
+
+def test_check_plan_mutation_mark_continuous_loop_completed():
+    content_before = (
+        "- [x] Open app\n"
+        "- [/] [Loop] Periodically monitor for new emails "
+        "(Exit: Continuous monitoring until manually stopped; Interval: every 5 minutes)\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    content_after = (
+        "- [x] Open app\n"
+        "- [x] [Loop] Periodically monitor for new emails "
+        "(Exit: Continuous monitoring until manually stopped; Interval: every 5 minutes)\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    res = check_plan_mutation_rejections(content_before, content_after)
+    assert res is not None
+    assert "cannot be unilaterally marked as completed [x]" in res
+
+
+def test_check_plan_mutation_user_stopped_allowed():
+    content_before = (
+        "- [x] Open app\n"
+        "- [/] [Loop] Periodically monitor for new emails "
+        "(Exit: Continuous monitoring until manually stopped; Interval: every 5 minutes)\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    content_after = (
+        "- [x] Open app\n"
+        "- [x] [Loop] Periodically monitor for new emails "
+        "(Exit: Continuous monitoring until manually stopped; Interval: every 5 minutes)\n"
+        "  - [x] Polling Check #1: Done"
+    )
+    state = MagicMock(spec=State)
+    state.injected_instruction = "Please stop the task now."
+    res = check_plan_mutation_rejections(content_before, content_after, state=state)
+    assert res is None
+
+
+def test_check_plan_mutation_normal_bounded_task():
+    content_before = "- [ ] Open Settings\n- [ ] Toggle WiFi"
+    content_after = "- [x] Open Settings\n- [x] Toggle WiFi"
+    res = check_plan_mutation_rejections(content_before, content_after)
+    assert res is None