remove: skin_tone_trace node type

- skin_tone is a person attribute (like height), not trace attribute
- Remove build_skin_tone_trace_nodes function
- Remove skin_tone_trace_nodes from TkgResult and API response
- Remove skin_tone_trace from documentation tables

src/api/trace_agent_api.rs

@@ -1002,7 +1002,6 @@ async fn rebuild_tkg(
                     "lip_track_nodes": r.lip_track_nodes,
                     "text_region_nodes": r.text_region_nodes,
                     "appearance_trace_nodes": r.appearance_trace_nodes,
-                    "skin_tone_trace_nodes": r.skin_tone_trace_nodes,
                     "accessory_nodes": r.accessory_nodes,
                     "object_nodes": r.object_nodes,
                     "hand_nodes": r.hand_nodes,

src/core/processor/tkg.rs

@@ -465,7 +465,6 @@ pub struct TkgResult {
     pub lip_track_nodes: usize,
     pub text_region_nodes: usize,
     pub appearance_trace_nodes: usize,
-    pub skin_tone_trace_nodes: usize,
     pub accessory_nodes: usize,
     pub object_nodes: usize,
     pub hand_nodes: usize,
@@ -511,7 +510,6 @@ pub async fn build_tkg(db: &PostgresDb, file_uuid: &str, output_dir: &str) -> Re
     let n_text = build_text_region_nodes(pool, file_uuid).await?;
     let n_appearance =
         build_appearance_trace_nodes(pool, file_uuid, output_dir, &pose_data).await?;
-    let n_skin_tone = build_skin_tone_trace_nodes(pool, file_uuid, output_dir).await?;
     let n_accessories = build_accessory_nodes(pool, file_uuid, output_dir).await?;
     let n_objects = build_yolo_object_nodes(pool, file_uuid, output_dir).await?;
     let n_hands = build_hand_nodes(pool, file_uuid, output_dir).await?;
@@ -532,7 +530,6 @@ pub async fn build_tkg(db: &PostgresDb, file_uuid: &str, output_dir: &str) -> Re
         lip_track_nodes: n_lip,
         text_region_nodes: n_text,
         appearance_trace_nodes: n_appearance,
-        skin_tone_trace_nodes: n_skin_tone,
         accessory_nodes: n_accessories,
         object_nodes: n_objects,
         hand_nodes: n_hands,
@@ -2578,94 +2575,6 @@ fn classify_fitzpatrick(h_mean: f64) -> &'static str {
     }
 }
 
-async fn build_skin_tone_trace_nodes(
-    pool: &PgPool,
-    file_uuid: &str,
-    output_dir: &str,
-) -> Result<usize> {
-    let nodes_table = t("tkg_nodes");
-    let fd_table = t("face_detections");
-    let mut count = 0;
-
-    let rows: Vec<(i64, i64)> = sqlx::query_as(&format!(
-        "SELECT trace_id::bigint, COUNT(*)::bigint \
-         FROM {} \
-         WHERE file_uuid = $1 AND trace_id IS NOT NULL \
-         GROUP BY trace_id",
-        fd_table
-    ))
-    .bind(file_uuid)
-    .fetch_all(pool)
-    .await?;
-
-    if rows.is_empty() {
-        tracing::info!("[TKG] No traced faces for skin_tone_trace nodes");
-        return Ok(0);
-    }
-
-    let path = Path::new(output_dir).join(format!("{}.face.json", file_uuid));
-    let face_json = if path.exists() {
-        let content = std::fs::read_to_string(&path)
-            .with_context(|| format!("Failed to read face.json: {}", path.display()))?;
-        serde_json::from_str::<serde_json::Value>(&content)?
-    } else {
-        tracing::warn!("[TKG] No face.json for skin_tone computation");
-        serde_json::Value::Null
-    };
-
-    for (trace_id, frame_count) in &rows {
-        let avg_skin_h = if !face_json.is_null() {
-            let mut skin_h_values = Vec::new();
-            if let Some(frames) = face_json.get("frames").and_then(|v| v.as_array()) {
-                for frame_entry in frames {
-                    if let Some(faces) = frame_entry.get("faces").and_then(|v| v.as_array()) {
-                        for face in faces {
-                            let face_trace_id = face.get("trace_id").and_then(|v| v.as_i64());
-                            if face_trace_id == Some(*trace_id) {
-                                skin_h_values.push(compute_skin_h_from_face(face));
-                            }
-                        }
-                    }
-                }
-            }
-            if skin_h_values.is_empty() {
-                20.0
-            } else {
-                skin_h_values.iter().sum::<f64>() / skin_h_values.len() as f64
-            }
-        } else {
-            20.0
-        };
-
-        let fitz_type = classify_fitzpatrick(avg_skin_h);
-        let external_id = format!("skin_tone_{}", trace_id);
-        let label = format!("Skin Tone Trace {}", trace_id);
-
-        sqlx::query(&format!(
-            "INSERT INTO {} (node_type, external_id, file_uuid, label, properties) \
-             VALUES ('skin_tone_trace', $1, $2, $3, $4::jsonb) \
-             ON CONFLICT (file_uuid, node_type, external_id) DO UPDATE SET properties = EXCLUDED.properties",
-            nodes_table
-        ))
-        .bind(&external_id)
-        .bind(file_uuid)
-        .bind(&label)
-        .bind(serde_json::json!({
-            "trace_id": trace_id,
-            "avg_skin_h": avg_skin_h,
-            "fitzpatrick_type": fitz_type,
-            "frame_count": frame_count,
-        }))
-        .execute(pool)
-        .await?;
-
-        count += 1;
-    }
-
-    tracing::info!("[TKG] Built {} skin_tone_trace nodes", count);
-    Ok(count)
-}
-
 // ── Accessory Nodes ──────────────────────────────────────────────
 
 async fn build_accessory_nodes(pool: &PgPool, file_uuid: &str, output_dir: &str) -> Result<usize> {
@@ -3219,7 +3128,6 @@ let r = TkgResult {
             lip_track_nodes: 4,
             text_region_nodes: 20,
             appearance_trace_nodes: 3,
-            skin_tone_trace_nodes: 5,
             accessory_nodes: 0,
             object_nodes: 10,
             hand_nodes: 0,