Remove shared tracker between cameras, fix task warning, add export script

- Remove shared DetectionTracker across cameras to prevent state leakage
- Add task="detect" to YOLO constructor to suppress warning
- Add export_engine.py script for .pt to .engine conversion
- Regenerate ONNX and TensorRT engine with latest settings

export_engine.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""Export a YOLO .pt model to TensorRT .engine.
+
+Usage:
+    python3 export_engine.py chicken-detection-model-v26n-300e-best-2026-05-02-NEW.pt
+    python3 export_engine.py model.pt --imgsz 640 --half --workspace 4
+"""
+
+from __future__ import annotations
+
+import argparse
+import sys
+from pathlib import Path
+
+
+def export_engine(
+    model_path: str | Path,
+    *,
+    imgsz: int = 640,
+    half: bool = True,
+    int8: bool = False,
+    batch: int = 1,
+    workspace: int = 4,     # GB
+    simplify: bool = True,
+    opset: int = 17,
+    verbose: bool = True,
+) -> str:
+    from ultralytics import YOLO
+
+    model = YOLO(model_path, task="detect")
+
+    output = model.export(
+        format="engine",
+        imgsz=imgsz,
+        half=half,
+        int8=int8,
+        batch=batch,
+        workspace=workspace,
+        simplify=simplify,
+        opset=opset,
+        verbose=verbose,
+    )
+
+    print(f"\nExported to: {output}")
+    return str(output)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Export YOLO .pt → TensorRT .engine")
+    parser.add_argument("model", help="Path to .pt model file")
+    parser.add_argument("--imgsz", type=int, default=640, help="Input image size (default: 640)")
+    parser.add_argument("--half", action="store_true", default=True, help="FP16 precision (default: on)")
+    parser.add_argument("--no-half", dest="half", action="store_false", help="FP32 precision")
+    parser.add_argument("--int8", action="store_true", help="INT8 quantization (needs calibration)")
+    parser.add_argument("--batch", type=int, default=1, help="Batch size (default: 1)")
+    parser.add_argument("--workspace", type=int, default=4, help="GPU workspace in GB (default: 4)")
+    parser.add_argument("--opset", type=int, default=17, help="ONNX opset version (default: 17)")
+    parser.add_argument("--quiet", action="store_true", help="Suppress verbose output")
+    args = parser.parse_args()
+
+    if not Path(args.model).exists():
+        print(f"error: model file not found: {args.model}", file=sys.stderr)
+        sys.exit(1)
+
+    export_engine(
+        args.model,
+        imgsz=args.imgsz,
+        half=args.half,
+        int8=args.int8,
+        batch=args.batch,
+        workspace=args.workspace,
+        opset=args.opset,
+        verbose=not args.quiet,
+    )
+
+
+if __name__ == "__main__":
+    main()