实现L1航向伺服(路线A1): 吊舱角度直入控制律 + 桥接胶水 + 干跑入口

- visual_track_control: ControlSnapshot 加可选 los_beta_deg/los_alpha_deg,
  第④步角度直入优先否则回退像素路径(向后兼容); config 拆出 load_from_dict 供内嵌复用
- pod_bridge: BridgeConfig 内嵌 TrackingConfig + 新 HeadingServoConfig;
  bridge._build_snapshot 合成 β/α(姿态来自PX4/角度来自吊舱,信号双路适配无电机),
  step 按 heading_servo.enabled 切 L1/L2, DEGRADED_HOLD 补发刹车保 offboard 心跳;
  run() 循环频率按生效律取(修 L1 频率错配)
- run_bridge.py: 闭环 CLI 入口, --dry-run(S2 只接吊舱不发offboard) 与实飞优雅停机
- 配置落 L1 首飞值(slow_approach/0.2mps、垂直压低、无电机仅用脱靶量)
- 新增测试 29 条(vtc5+config9+bridgeL1 10+runner5); 全量 401 passed

utils/tests/pod_bridge/config_test.py

@@ -5,8 +5,9 @@ from pathlib import Path
 
 import pytest
 
-from pod_bridge.config import (BridgeConfig, GuidanceConfig, PodSerialConfig,
-                               load_from_json)
+from pod_bridge.config import (BridgeConfig, GuidanceConfig, HeadingServoConfig,
+                               PodSerialConfig, load_from_json)
+from visual_track_control.config import NoDistanceAction, TrackingConfig
 
 _DEFAULT_CONFIG = Path(__file__).resolve().parents[2] / "config" / "pod_bridge.json"
 
@@ -113,3 +114,59 @@ def test_out_of_range_raises(tmp_path, obj, field):
 
 def test_pod_serial_default_port_is_placeholder():
     assert PodSerialConfig().port == ""
+
+
+# --- L1 航向伺服配置（方案 §4，决策 1/2/3）----------------------------------
+def test_empty_json_heading_servo_and_tracking_default(tmp_path):
+    cfg = load_from_json(_write(tmp_path, {}))
+    assert cfg.heading_servo == HeadingServoConfig()
+    assert cfg.heading_servo.enabled is False      # 默认关，保持 L2 行为
+    assert cfg.tracking == TrackingConfig()        # 缺 tracking 段 → 默认
+
+
+def test_heading_servo_loads():
+    cfg = load_from_json(str(_DEFAULT_CONFIG))
+    hs = cfg.heading_servo
+    assert hs.enabled is True                       # 部署配置走 L1
+    assert hs.beta_from_off_target is True          # 无电机：脱靶量为主信号
+    assert hs.beta_from_frame is False              # 框架角当前无用
+    assert hs.vertical_enabled is True              # 决策3：无人机 L1 开垂直
+
+
+def test_heading_servo_partial_override(tmp_path):
+    cfg = load_from_json(_write(tmp_path, {
+        "heading_servo": {"beta_sign": -1, "beta_from_frame": True},
+    }))
+    assert cfg.heading_servo.beta_sign == -1
+    assert cfg.heading_servo.beta_from_frame is True
+    assert cfg.heading_servo.alpha_sign == 1        # 默认回退
+
+
+@pytest.mark.parametrize("obj,field", [
+    ({"heading_servo": {"beta_sign": 0}}, "heading_servo.beta_sign"),   # 非 ±1
+    ({"heading_servo": {"alpha_sign": 2}}, "heading_servo.alpha_sign"),
+    ({"heading_servo": {"beta_sign": 1.0}}, "heading_servo.beta_sign"),  # 非整数
+    ({"heading_servo": {"unknown": 1}}, "未知字段"),
+])
+def test_heading_servo_bad_sign_rejected(tmp_path, obj, field):
+    with pytest.raises(ValueError, match=field.replace(".", r"\.")):
+        load_from_json(_write(tmp_path, obj))
+
+
+def test_tracking_incomplete_section_raises(tmp_path):
+    # tracking 段一旦提供即按 vtc 严格解析：缺分组报错
+    with pytest.raises(ValueError, match="camera"):
+        load_from_json(_write(tmp_path, {"tracking": {
+            "control": {"frequency_hz": 20.0, "visual_stale_ms": 200,
+                        "distance_stale_ms": 500, "attitude_stale_ms": 300},
+        }}))
+
+
+def test_shipped_tracking_l1_values():
+    cfg = load_from_json(str(_DEFAULT_CONFIG))
+    d = cfg.tracking.distance
+    assert d.no_distance_action is NoDistanceAction.SLOW_APPROACH  # 决策3：低速接近
+    assert d.no_distance_approach_limit_mps == pytest.approx(0.2)  # 极低限速
+    assert cfg.tracking.vertical.vz_limit_mps == pytest.approx(0.5)  # vz 压低
+    assert cfg.tracking.heading.mode.value == "rate"
+