feat: 添加多摄像头测试工具，支持实时预览和快照功能

xr_rm_bringup/test/camera_test_output/.gitignore

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+*
+!.gitignore

xr_rm_bringup/test/test_realsense_multi_camera.py

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+from __future__ import annotations
+
+import importlib.util
+from pathlib import Path
+import sys
+
+import pytest
+
+
+MODULE_PATH = (
+    Path(__file__).resolve().parents[1]
+    / "tools"
+    / "realsense_multi_camera_test.py"
+)
+SPEC = importlib.util.spec_from_file_location("realsense_multi_camera_test", MODULE_PATH)
+assert SPEC is not None and SPEC.loader is not None
+camera_test = importlib.util.module_from_spec(SPEC)
+sys.modules[SPEC.name] = camera_test
+SPEC.loader.exec_module(camera_test)
+
+
+def devices() -> list[camera_test.DeviceInfo]:
+    return [
+        camera_test.DeviceInfo("Intel RealSense D405", "D405", "412622272532", "3.2"),
+        camera_test.DeviceInfo("Intel RealSense D455", "D455", "234222303366", "3.2"),
+        camera_test.DeviceInfo("Intel RealSense D405", "D405", "260322272273", "3.2"),
+    ]
+
+
+def test_assigns_camera_roles_with_and_without_left_serial() -> None:
+    unidentified = camera_test.assign_camera_roles(devices(), None)
+    assert [camera.role for camera in unidentified] == ["GLOBAL", "D405-A", "D405-B"]
+    assert [camera.serial for camera in unidentified[1:]] == ["260322272273", "412622272532"]
+
+    identified = camera_test.assign_camera_roles(devices(), "412622272532")
+    assert {camera.role: camera.serial for camera in identified} == {
+        "GLOBAL": "234222303366",
+        "LEFT": "412622272532",
+        "RIGHT": "260322272273",
+    }
+
+
+def test_rejects_invalid_camera_selection() -> None:
+    with pytest.raises(ValueError, match="左臂序列号"):
+        camera_test.assign_camera_roles(devices(), "missing")
+
+    with pytest.raises(ValueError, match="2 台 D405 和 1 台 D455"):
+        camera_test.assign_camera_roles(devices()[:-1], None)
+
+
+def test_counts_frame_number_gaps() -> None:
+    stats = camera_test.FrameStats(target_fps=30, start_time=0.0)
+    stats.update(10, 0.0)
+    stats.update(11, 1.0 / 30.0)
+    stats.update(14, 2.0 / 30.0)
+
+    assert stats.received == 3
+    assert stats.dropped == 2
+    assert stats.drop_rate == pytest.approx(0.4)
+    assert stats.average_fps(2.0 / 30.0) == pytest.approx(30.0)
+
+
+def test_snapshot_names_follow_camera_roles() -> None:
+    identified = camera_test.assign_camera_roles(devices(), "412622272532")
+    assert camera_test.snapshot_filenames(identified) == {
+        "234222303366": "global.png",
+        "412622272532": "left.png",
+        "260322272273": "right.png",
+    }
+
+    unidentified = camera_test.assign_camera_roles(devices(), None)
+    assert camera_test.snapshot_filenames(unidentified) == {
+        "234222303366": "global.png",
+        "260322272273": "d405_260322272273.png",
+        "412622272532": "d405_412622272532.png",
+    }