test: guard locomotion grounding exemption (and no static over-suppression)

Asserts the airborne-swing exemption removes box-step's large phase-transition
heel floats, and that superhero-landing's genuine static heel-lift is still
flagged (the exemption must not suppress real artifacts).

Author: a-baran-orhan

packages/posecode-eval/test/locomotion-grounding.test.ts

@@ -0,0 +1,47 @@
+import { describe, it, expect } from "vitest";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, resolve } from "node:path";
+import { probeMovement } from "../src/index.js";
+
+const examplesDir = resolve(
+  dirname(fileURLToPath(import.meta.url)),
+  "../../../spec/examples",
+);
+const load = (name: string): string =>
+  readFileSync(resolve(examplesDir, `${name}.posecode`), "utf8");
+
+const footWarnings = (name: string) =>
+  probeMovement(load(name)).diagnostics.warnings.filter((w) =>
+    ["heel-height", "toe-height", "sole-angle", "grounding-rom-conflict"].includes(w.kind),
+  );
+
+/**
+ * A stance foot in a traveling clip rolls onto its ball as the body passes
+ * (push-off) and is briefly airborne at each step transition — correct gait,
+ * not a grounding artifact, so it is exempt from the static flat-foot checks.
+ * A static clip keeps the strict bar, so genuine heel-lift must still surface.
+ */
+describe("locomotion grounding exemption", () => {
+  it("exempts a locomotion stance foot's airborne swing (no large float at a step transition)", () => {
+    // Before the fix, box-step's stance pin was measured while it was still
+    // descending from the previous phase's swing — a ~0.12m heel float and a
+    // ~33° sole tilt mid-transition. The airborne-swing exemption removes those
+    // large phase-transition floats (a smaller settling roll may remain).
+    const large = footWarnings("box-step").filter(
+      (w) =>
+        (w.kind === "heel-height" && w.value > 0.1) ||
+        (w.kind === "sole-angle" && w.value > 30),
+    );
+    expect(large, large.map((w) => w.detail).join("\n")).toHaveLength(0);
+  });
+
+  it("still flags genuine heel-lift in a static deep pose (no over-suppression)", () => {
+    // superhero-landing holds a deep static landing whose shin exceeds the ankle
+    // dorsiflexion ROM; that heel-lift is a real artifact and must stay flagged.
+    const warns = footWarnings("superhero-landing");
+    expect(warns.some((w) => w.kind === "grounding-rom-conflict" || w.kind === "heel-height")).toBe(
+      true,
+    );
+  });
+});