精简仓库结构并增强任务链路：归档双目可选后端、新增LOS判据与自定义返航

归档 legacy/：stereo_yolo/stereo_ranger/target_tracker 三包 + 175 条测试 + demo/配置/权重/三份规格；运行链路不再依赖，默认 pytest 446 条，归档测试按需运行。

目标有效性第二判据改为 LOS 运动学一致性（pod_bridge/los_consistency.py），删除 require_vision；pod_locked() 叠加该判据，状态机随之后退重搜。

自定义返航（task_runner/return_home.py）：保持转场高度回起飞点 → 恢复初始航向 → 垂直降落，不再爬 RTL_RETURN_ALT；未起飞/无起飞点/超时/异常仍退回 PX4 原生 RTL。

任务链安全兜底：主循环异常→紧急返航、stop 幂等、landing_stop 保留遥测、in_air 流复用+超时、解锁/起飞与吊舱识别仅执行一次、rtl_timeout 上限。

入口共享件拆到 utils/sitl_support.py；pod_sitl_test.py→l1_sitl_test.py；删除旧架构 test.py；相机脚本移入 tools/。

新增 .gitignore 并剔除历史误跟踪的 59 个 .pyc；requirements 按实际依赖重写；文档全面对齐，新增 legacy/README.md 与 tools/README.md。

utils/tests/ground_station/video_source_test.py

@@ -0,0 +1,138 @@
+"""video_source_test.py —— RTSP→MJPEG 视频源单元测试（注入假采集器，不依赖真流）。
+
+覆盖：拉帧→JPEG 编码缓存、宽度限制（等比缩放）、断线重连（重新调用工厂）、
+打开失败退避重试、online 判定、MJPEG 分块格式。
+"""
+
+import sys
+import time
+from pathlib import Path
+
+import numpy as np
+
+_ROOT = Path(__file__).resolve().parents[3]   # utils/tests/ground_station → 仓库根
+if str(_ROOT) not in sys.path:
+    sys.path.insert(0, str(_ROOT))
+
+from ground_station.video_source import RtspVideoSource  # noqa: E402
+
+
+class FakeCapture:
+    """假采集器：可注入读失败次数；帧为纯色小图。"""
+
+    def __init__(self, fail_reads=0, height=60, width=120):
+        self.fail_reads = fail_reads
+        self._frame = np.full((height, width, 3), 128, dtype=np.uint8)
+        self.released = False
+
+    def isOpened(self):
+        return True
+
+    def read(self):
+        if self.fail_reads > 0:
+            self.fail_reads -= 1
+            return False, None
+        return True, self._frame
+
+    def release(self):
+        self.released = True
+
+
+def _wait(pred, timeout_s=4.0, step=0.02):
+    t0 = time.monotonic()
+    while time.monotonic() - t0 < timeout_s:
+        if pred():
+            return True
+        time.sleep(step)
+    return False
+
+
+def _decode(jpeg):
+    import cv2
+    return cv2.imdecode(np.frombuffer(jpeg, dtype=np.uint8), cv2.IMREAD_COLOR)
+
+
+def test_frames_encoded_and_online():
+    src = RtspVideoSource("rtsp://fake", width=120, fps=50,
+                          capture_factory=lambda: FakeCapture())
+    assert src.online is False                  # 尚无帧 → 离线
+    src.start()
+    try:
+        assert _wait(lambda: src.latest()[1] is not None)
+        seq, jpeg = src.latest()
+        assert seq >= 1
+        assert jpeg[:2] == b"\xff\xd8"          # JPEG SOI 头
+        assert _decode(jpeg).shape[1] == 120    # 宽度不超限
+        assert src.online is True
+    finally:
+        src.stop()
+
+
+def test_downscale_to_max_width():
+    src = RtspVideoSource("rtsp://fake", width=60, fps=50,
+                          capture_factory=lambda: FakeCapture(height=60, width=120))
+    src.start()
+    try:
+        assert _wait(lambda: src.latest()[1] is not None)
+        img = _decode(src.latest()[1])
+        assert img.shape[1] == 60 and img.shape[0] == 30   # 等比缩到 60 宽
+    finally:
+        src.stop()
+
+
+def test_reconnect_after_read_failure():
+    opened = []
+
+    def factory():
+        cap = FakeCapture(fail_reads=(10 ** 6 if not opened else 0))
+        opened.append(cap)
+        return cap
+
+    src = RtspVideoSource("rtsp://fake", width=120, fps=50,
+                          capture_factory=factory)
+    src.start()
+    try:
+        assert _wait(lambda: src.latest()[1] is not None, timeout_s=5.0)
+        assert len(opened) >= 2                 # 首采集器读失败 → 重新打开
+        assert opened[0].released is True
+    finally:
+        src.stop()
+
+
+def test_open_failure_keeps_retrying():
+    calls = []
+
+    class ClosedCapture:
+        def isOpened(self):
+            return False
+
+        def release(self):
+            pass
+
+    def factory():
+        calls.append(1)
+        return ClosedCapture()
+
+    src = RtspVideoSource("rtsp://fake", capture_factory=factory)
+    src.start()
+    try:
+        assert _wait(lambda: len(calls) >= 2, timeout_s=4.0)  # 1s 退避后重试
+        assert src.latest()[1] is None
+    finally:
+        src.stop()
+
+
+def test_mjpeg_stream_chunks():
+    src = RtspVideoSource("rtsp://fake", width=120, fps=50,
+                          capture_factory=lambda: FakeCapture())
+    src.start()
+    try:
+        assert _wait(lambda: src.latest()[1] is not None)
+        gen = src.mjpeg_stream()
+        chunk = next(gen)
+        assert chunk.startswith(b"--frame\r\nContent-Type: image/jpeg\r\n")
+        assert b"Content-Length: " in chunk
+        assert chunk.endswith(b"\r\n")
+        gen.close()
+    finally:
+        src.stop()