feat(v1): relax fall sensitivity for low overhead cameras

Adds configurable event.require_rapid_drop (default off), require_lower_body
(default off) and horizontal_angle_threshold_degrees (default 45). With the
lenient defaults a sustained horizontal pose alone enters SUSPECT and confirms
after the confirm window, which is now the main false-positive guard; missing
knees/ankles no longer reject the pose. Thresholds flow into config_version.
End-to-end smoke confirms a lying pose; 70 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v1/config.py

@@ -69,6 +69,9 @@ class EventConfig:
     confirm_window_seconds: float
     recovery_window_seconds: float
     cooldown_seconds: float
+    require_rapid_drop: bool = False
+    require_lower_body: bool = False
+    horizontal_angle_threshold_degrees: float = 45.0
 
 
 @dataclass(frozen=True)
@@ -105,6 +108,9 @@ class AppConfig:
                 "confirm_window_seconds": self.event.confirm_window_seconds,
                 "recovery_window_seconds": self.event.recovery_window_seconds,
                 "cooldown_seconds": self.event.cooldown_seconds,
+                "require_rapid_drop": self.event.require_rapid_drop,
+                "require_lower_body": self.event.require_lower_body,
+                "horizontal_angle_threshold_degrees": self.event.horizontal_angle_threshold_degrees,
             },
         }
         canonical = json.dumps(payload, sort_keys=True, separators=(",", ":"))
@@ -139,6 +145,12 @@ def _number(value: Any, field_name: str, minimum: float, maximum: float) -> floa
     return result
 
 
+def _bool(value: Any, field_name: str) -> bool:
+    if not isinstance(value, bool):
+        raise ConfigError("{0} must be a boolean".format(field_name))
+    return value
+
+
 def _resolve_path(config_path: Path, value: Any, field_name: str) -> Path:
     raw_path = Path(_text(value, field_name))
     if raw_path.is_absolute():
@@ -274,6 +286,14 @@ def load_config(path: Path) -> AppConfig:
             0.0,
             3600.0,
         ),
+        require_rapid_drop=_bool(event_raw.get("require_rapid_drop", False), "event.require_rapid_drop"),
+        require_lower_body=_bool(event_raw.get("require_lower_body", False), "event.require_lower_body"),
+        horizontal_angle_threshold_degrees=_number(
+            event_raw.get("horizontal_angle_threshold_degrees", 45.0),
+            "event.horizontal_angle_threshold_degrees",
+            0.0,
+            90.0,
+        ),
     )
 
     artifacts = _mapping(root.get("artifacts"), "artifacts")