Kernel rig: construct.plane.axis_point gets construction cases

The plane through a box edge and its far corner, graded against its
closed-form normal (0,-2,3)/sqrt(13) through the origin, and the refusal
of a point on the axis.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DtL5M41G8Nua7HvuFPZkmJ

tests/kernel-cases/construction/cov-plane-axis-point-box-edge-and-far-corner/expected.json

@@ -0,0 +1,22 @@
+{
+ "sources": [],
+ "what": "the plane through a box edge and the corner farthest from it",
+ "source": "analytic",
+ "method": "box 40 x 30 x 20 with a corner at the origin: the edge y 0, z 0 is the X axis and the far corner is (40,30,20); the plane holds the origin and its normal is X x (0,30,20) = (0,-20,30), i.e. (0,-2,3)/sqrt(13): the plane 3z = 2y, which also holds the opposite edge's other end (0,30,20)",
+ "construction": {
+  "P": {
+   "plane": {
+    "through": [
+     0,
+     30,
+     20
+    ],
+    "normal": [
+     0.0,
+     -0.5547,
+     0.83205
+    ]
+   }
+  }
+ }
+}

tests/kernel-cases/construction/cov-plane-axis-point-box-edge-and-far-corner/recipe.json

@@ -0,0 +1,33 @@
+{
+ "commands": [
+  {
+   "command": "solid.box",
+   "params": {
+    "length": 40,
+    "width": 30,
+    "height": 20,
+    "body_name": "Box"
+   }
+  },
+  {
+   "command": "construct.plane.axis_point",
+   "params": {
+    "axis": {
+     "edge": [
+      20,
+      0,
+      0
+     ]
+    },
+    "point": {
+     "vertex": [
+      40,
+      30,
+      20
+     ]
+    },
+    "name": "P"
+   }
+  }
+ ]
+}

tests/kernel-cases/construction/cov-plane-axis-point-refuses-a-point-on-the-axis/expected.json

@@ -0,0 +1,8 @@
+{
+ "sources": [],
+ "what": "a plane through the Z axis and a point on it",
+ "source": "analytic",
+ "method": "(0,0,50) is on the Z axis: every plane through the axis holds it, so no one plane is meant: refused",
+ "outcome": "refused",
+ "refusal": "point is on the axis"
+}

tests/kernel-cases/construction/cov-plane-axis-point-refuses-a-point-on-the-axis/recipe.json

@@ -0,0 +1,20 @@
+{
+ "commands": [
+  {
+   "command": "construct.plane.axis_point",
+   "params": {
+    "axis": {
+     "axis": "Z"
+    },
+    "point": {
+     "point": [
+      0,
+      0,
+      50
+     ]
+    },
+    "name": "P"
+   }
+  }
+ ]
+}