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/utils/test_coordinates_sequence.py

@@ -0,0 +1,105 @@
+# 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.
+
+"""Unit tests for sequence coordinate normalization and overlay visualization."""
+
+import io
+from PIL import Image
+from artemis.utils.coordinates import normalize_step_actions
+from artemis.utils.visualization import draw_action_overlay_on_image
+
+
+def test_normalize_step_actions_click_sequence_does_not_inherit_single_action():
+    """Verify that click_sequence does NOT inherit single coordinates from action_taken."""
+    step_dict = {
+        "step_id": "step-123",
+        "action_taken": [
+            {
+                "action": "tap",
+                "coordinates": [540, 720],
+                "normalized_coordinates": [500, 300],
+            }
+        ],
+        "generic_tools": [
+            {
+                "name": "click_sequence",
+                "payload": {
+                    "args": {
+                        "sequence": "[[500, 300], [876, 360]]",
+                        "delay_ms": "50",
+                    },
+                    "result": {
+                        "status": "success",
+                        "outcome": "Sequence clicked successfully: Tapped at [540, 720]; Tapped at [946, 864]",
+                    },
+                },
+            }
+        ],
+        "extra_metadata": {"width": 1080, "height": 2400},
+    }
+
+    normalized = normalize_step_actions(step_dict)
+    tool = normalized["generic_tools"][0]
+    args = tool["payload"]["args"]
+
+    # Coordinates from first_act must NOT be injected into click_sequence
+    assert "coordinates" not in args or args.get("coordinates") is None
+    assert "normalized_coordinates" not in args or args.get("normalized_coordinates") is None
+
+    # Sequence must be parsed into a list and normalized
+    assert args["sequence"] == [[500, 300], [876, 360]]
+    assert args["normalized_sequence"] == [[500, 300], [876, 360]]
+
+
+def test_normalize_step_actions_physical_sequence():
+    """Verify that physical coordinates in sequence are converted into normalized_sequence."""
+    step_dict = {
+        "step_id": "step-456",
+        "action_taken": [],
+        "generic_tools": [
+            {
+                "name": "click_sequence",
+                "payload": {
+                    "args": {
+                        "sequence": [[540, 1200], [1080, 2400]],
+                    }
+                },
+            }
+        ],
+        "extra_metadata": {"width": 1080, "height": 2400},
+    }
+
+    normalized = normalize_step_actions(step_dict)
+    args = normalized["generic_tools"][0]["payload"]["args"]
+
+    assert args["normalized_sequence"] == [[500, 500], [1000, 1000]]
+
+
+def test_draw_action_overlay_click_sequence():
+    """Verify PIL overlay drawing for click_sequence with stringified sequence."""
+    img = Image.new("RGB", (1080, 2400), color="blue")
+    buf = io.BytesIO()
+    img.save(buf, format="JPEG")
+    raw_bytes = buf.getvalue()
+
+    action_args = {
+        "sequence": "[[500, 300], [876, 360]]",
+    }
+
+    annotated_bytes = draw_action_overlay_on_image(raw_bytes, "click_sequence", action_args)
+    assert annotated_bytes is not None
+    assert len(annotated_bytes) > 0
+
+    res_img = Image.open(io.BytesIO(annotated_bytes))
+    assert res_img.size == (1080, 2400)