test(cog-pose): verify weights load and produce valid 17-keypoint output

Strengthen `real_weights_load_when_available` in the smoke suite:

- search for `pose_v1.safetensors` under the three plausible test
  cwds (crate dir, `v2/`, repo root) so the test exercises the real
  loader regardless of where `cargo test` is invoked from
- after inference, chunk the flat 34-scalar output into 17 (x, y)
  pairs and assert each pair is finite, non-NaN, and inside the
  sigmoid range [0, 1]
- keep the skip path with a clear message when the safetensors blob
  isn't on disk (so the suite still passes on a fresh appliance
  install where weights ship separately)

This complements the inline unit tests in `src/inference.rs` — those
exercise the loader / forward-pass plumbing, the smoke test exercises
the public crate surface.

v2/crates/cog-pose-estimation/tests/smoke.rs

@@ -40,12 +40,22 @@ fn engine_rejects_wrong_shape_input() {
 #[test]
 fn real_weights_load_when_available() {
     use cog_pose_estimation::inference::InferenceEngine;
-    let weights = std::path::Path::new("cog/artifacts/pose_v1.safetensors");
-    if !weights.exists() {
+    // Search the cwds a `cargo test` invocation can land in
+    // (workspace root, `v2/`, or the crate dir).
+    let candidates = [
+        "cog/artifacts/pose_v1.safetensors",
+        "crates/cog-pose-estimation/cog/artifacts/pose_v1.safetensors",
+        "v2/crates/cog-pose-estimation/cog/artifacts/pose_v1.safetensors",
+    ];
+    let Some(weights) = candidates
+        .iter()
+        .map(std::path::Path::new)
+        .find(|p| p.exists())
+    else {
         // Skip when running outside the repo (e.g. on a fresh appliance install).
-        eprintln!("(skipping — cog/artifacts/pose_v1.safetensors not present in cwd)");
+        eprintln!("(skipping — pose_v1.safetensors not present under any known cwd)");
         return;
-    }
+    };
     let engine = InferenceEngine::with_weights(Some(weights)).expect("load real weights");
     assert!(
         engine.backend().starts_with("candle-"),
@@ -54,6 +64,27 @@ fn real_weights_load_when_available() {
     );
     let out = engine.infer(&SyntheticInput.as_window()).expect("infer");
     assert!(out.is_finite());
+
+    // Chunked into 17 (x, y) pairs — every coordinate must be finite and
+    // sit inside the sigmoid output range. This is the "real wiring"
+    // assertion the README points at.
+    let pairs: Vec<[f32; 2]> = out
+        .keypoints
+        .chunks_exact(2)
+        .map(|c| [c[0], c[1]])
+        .collect();
+    assert_eq!(pairs.len(), OUTPUT_KEYPOINTS);
+    for (i, [x, y]) in pairs.iter().enumerate() {
+        assert!(
+            x.is_finite() && y.is_finite() && !x.is_nan() && !y.is_nan(),
+            "keypoint {i} bad: ({x}, {y})"
+        );
+        assert!(
+            (0.0..=1.0).contains(x) && (0.0..=1.0).contains(y),
+            "keypoint {i} out of [0, 1]: ({x}, {y})"
+        );
+    }
+
     // Real model emits the published validation PCK@50 as its self-reported
     // confidence — stub returns 0.0. This is the key assertion that proves
     // the cog isn't silently falling back to the stub.