Jets: freeze origins, guard set_body, fine-boundary hit helper

Sector/Tube/Radial store origin as a validated float 2-tuple, so caller
lists/arrays cannot change a registered definition. Simulation.set_body
rejects nonzero motion for bodies with Jet-driven links once initialized
(before initialize the sync-time stationary check applies).
prepare_fine_boundary accepts jets in the same coarse cell-edge frame as
fine objects, records read-only FP64 edge-frame hits (FineBoundary2D
.curved_hits, default None) and rejects empty or overlapping selections
before CUDA. FixedPatchStepper wiring is not included.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/CelerisLab/body/jets.py

@@ -32,6 +32,15 @@ def _finite(*values):
         raise ValueError("Jet parameters must be finite")
 
 
+def _freeze_origin(spec):
+    """Store ``origin`` as a validated float 2-tuple (no caller-owned list/array)."""
+    origin = tuple(float(v) for v in spec.origin)
+    if len(origin) != 2:
+        raise ValueError("Jet origin must be a 2D point")
+    _finite(*origin)
+    object.__setattr__(spec, "origin", origin)
+
+
 @dataclass(frozen=True)
 class Sector:
     """Annular sector about ``origin``: |angle offset| < half_width, r_min <= r <= r_max."""
@@ -42,7 +51,8 @@ class Sector:
     r_min: float = 0.0
 
     def __post_init__(self):
-        _finite(*self.origin, self.angle, self.half_width, self.r_max, self.r_min)
+        _freeze_origin(self)
+        _finite(self.angle, self.half_width, self.r_max, self.r_min)
         if not (0 < self.half_width <= math.pi and 0 <= self.r_min <= self.r_max):
             raise ValueError("Sector requires 0 < half_width <= pi and 0 <= r_min <= r_max")
 
@@ -63,7 +73,8 @@ class Tube:
     half_width: float
 
     def __post_init__(self):
-        _finite(*self.origin, self.axis_angle, self.length, self.half_width)
+        _freeze_origin(self)
+        _finite(self.axis_angle, self.length, self.half_width)
         if self.length <= 0 or self.half_width <= 0:
             raise ValueError("Tube requires positive length and half_width")
 
@@ -82,7 +93,7 @@ class Radial:
     inward: bool = True
 
     def __post_init__(self):
-        _finite(*self.origin)
+        _freeze_origin(self)
 
     def direction(self, hits):
         d = hits - np.asarray(self.origin, np.float64)