Implement Apex Agent MVP scaffold

tools/describe_screen.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from core.device_manager import DeviceManager
+from core.models import Scene
+from tools._device import get_driver
+from vision.ocr import PaddleOCREngine, run_ocr
+from vision.scene_builder import build_scene, infer_png_size
+from vision.ui_parser import parse_ui_tree
+
+
+def describe_screen(
+    device_id: str | None = None,
+    *,
+    manager: DeviceManager | None = None,
+    ocr_engine: PaddleOCREngine | None = None,
+) -> Scene:
+    driver = get_driver(device_id, manager=manager)
+    screenshot = driver.screenshot()
+    raw_tree = driver.tree()
+    width, height = infer_png_size(screenshot)
+    return build_scene(
+        screen_width=width,
+        screen_height=height,
+        ui_elements=parse_ui_tree(raw_tree),
+        ocr_elements=run_ocr(screenshot, engine=ocr_engine),
+    )
+