fix(cog-pose-estimation): emit frames under default config (ADR-159 A1)

pose_v1 has no confidence head, so infer() emits a constant 0.185 per
frame. The config default_min_confidence was 0.3 and the runtime gates
on confidence >= min_confidence, so a default install silently emitted
ZERO pose.frame events while health reported healthy.

- Add inference::MODEL_TYPICAL_CONFIDENCE (0.185, the validation PCK@50)
  as the single published per-frame confidence.
- Pin default_min_confidence() to MODEL_TYPICAL_CONFIDENCE so a default
  install clears its own gate and emits.
- Warn at run.started when min_confidence exceeds the model typical
  confidence (disclosed, not silent); document the trade-off in the
  config field, the JSON schema, and inference.rs.

Failing-on-old test: default_config_emits_frames_with_real_model
(with old 0.3 it panics: "default install would emit zero pose.frame
events").

Co-Authored-By: claude-flow <ruv@ruv.net>

v2/crates/cog-pose-estimation/src/config.rs

@@ -23,6 +23,13 @@ pub struct CogConfig {
     pub poll_ms: u64,
 
     /// Confidence threshold below which a frame's keypoints are not emitted.
+    ///
+    /// Defaults to [`crate::inference::MODEL_TYPICAL_CONFIDENCE`] (0.185) — the
+    /// model's published per-frame confidence. `pose_v1` has no confidence head,
+    /// so every frame carries this same value; a default above it would silently
+    /// suppress *all* `pose.frame` events while health still reports healthy.
+    /// The runtime warns at `run.started` if this is raised above the model's
+    /// typical confidence rather than dropping frames quietly.
     #[serde(default = "default_min_confidence")]
     pub min_confidence: f32,
 }
@@ -36,7 +43,9 @@ fn default_poll_ms() -> u64 {
 }
 
 fn default_min_confidence() -> f32 {
-    0.3
+    // Pinned to the model's typical/published confidence so a default install
+    // actually emits frames. See `min_confidence` doc and ADR-159 §A1.
+    crate::inference::MODEL_TYPICAL_CONFIDENCE
 }
 
 impl CogConfig {

v2/crates/cog-pose-estimation/src/inference.rs

@@ -27,6 +27,16 @@ pub const INPUT_SUBCARRIERS: usize = 56;
 pub const INPUT_TIMESTEPS: usize = 20;
 pub const OUTPUT_KEYPOINTS: usize = 17;
 
+/// The model's typical self-reported confidence. `pose_v1` has **no confidence
+/// head** (the head emits 34 keypoint coordinates only), so per-frame confidence
+/// is not available from the network. This is the validation-set PCK@50 (18.5%)
+/// the training run reported, used as the published per-frame confidence floor.
+///
+/// Surfaced as a public constant so the runtime can warn when a configured
+/// `min_confidence` threshold exceeds it — otherwise a default install would
+/// silently emit zero `pose.frame` events while health reports healthy.
+pub const MODEL_TYPICAL_CONFIDENCE: f32 = 0.185;
+
 #[derive(Debug, Clone)]
 pub struct CsiWindow {
     pub data: Vec<f32>, // length INPUT_SUBCARRIERS * INPUT_TIMESTEPS
@@ -283,12 +293,15 @@ impl InferenceEngine {
         let out = model.net.forward(&t)?; // [1, 34]
         let flat: Vec<f32> = out.flatten_all()?.to_vec1()?;
         // Confidence from pose_v1 is a published constant rather than per-frame —
-        // the trained model didn't emit a confidence head. Use the validation-set
-        // PCK@50 (18.5%) as the published self-reported confidence so downstream
-        // consumers can gate display decisions on it.
+        // the trained model has no confidence head (the head emits 34 keypoint
+        // coordinates only), so a real per-frame value is genuinely unavailable.
+        // We surface the validation-set PCK@50 (`MODEL_TYPICAL_CONFIDENCE`) as the
+        // honest self-reported confidence. The runtime's `min_confidence` default
+        // is pinned at or below this so a default install actually emits frames
+        // (and warns if an operator raises the threshold above the model's reach).
         Ok(PoseOutput {
             keypoints: flat,
-            confidence: 0.185,
+            confidence: MODEL_TYPICAL_CONFIDENCE,
         })
     }
 }

v2/crates/cog-pose-estimation/src/main.rs

@@ -113,6 +113,18 @@ fn cmd_run(
     let cfg = CogConfig::load(&config_path)?;
     emit_event(&Event::run_started(COG_ID, &cfg));
 
+    // Disclosure: pose_v1 has no confidence head, so every frame carries the
+    // same `MODEL_TYPICAL_CONFIDENCE`. A `min_confidence` above that silently
+    // suppresses *all* pose.frame events. Warn loudly rather than drop quietly.
+    if cfg.min_confidence > cog_pose_estimation::inference::MODEL_TYPICAL_CONFIDENCE {
+        tracing::warn!(
+            min_confidence = cfg.min_confidence,
+            model_typical_confidence = cog_pose_estimation::inference::MODEL_TYPICAL_CONFIDENCE,
+            "configured min_confidence exceeds the model's typical confidence; \
+             no pose.frame events will be emitted until this is lowered"
+        );
+    }
+
     let engine = InferenceEngine::with_adapter(adapter.as_deref())?;
     if engine.is_calibrated() {
         tracing::info!("per-room calibration adapter loaded");