feat: unified config.yaml with extensible model presets (A-D data-driven, E/F ready)

- config.yaml canonical for stream/models/counting/batch/output/camera
- models.modes hold engines+class filters only; conf/iou/min_bbox in detection_params
- predict.py derives tracker roles structurally (no per-mode branching)
- dashboard mode switch validates + persists atomically to config.yaml
- .env keeps secrets/deployment only; zones.json geometry; tracker.yaml hyperparams
- batch_mode.json keeps manual/auto batch mode; legacy model_mode ignored w/ warning
- src/detection+tracking gain iou param (default 0.7 = no behavior change)

tests/test_config_loader.py

@@ -0,0 +1,128 @@
+"""Smoke tests for src/config_loader.py — pure-Python, no cv2/ultralytics needed."""
+
+import json
+import os
+
+import pytest
+import yaml
+
+from src.config_loader import (
+    check_legacy_batch_mode,
+    load_config,
+    read_zone_polygons,
+    resolve_active_mode,
+    set_active_mode,
+    validate_config,
+)
+
+
+@pytest.fixture()
+def repo_config_path():
+    p = os.path.join(os.path.dirname(os.path.dirname(__file__)), "config.yaml")
+    assert os.path.exists(p), "repo config.yaml missing"
+    return p
+
+
+def test_repo_config_loads_and_validates(repo_config_path):
+    cfg = load_config(repo_config_path)
+    assert cfg.models.active_mode == "C"
+    assert set(cfg.models.modes) >= {"A", "B", "C", "D"}
+    for mode_id, mode in cfg.models.modes.items():
+        assert mode.engines, f"mode {mode_id} has no engines"
+        for e in mode.engines:
+            assert e.path in cfg.models.paths, f"mode {mode_id}: unknown engine {e.path}"
+            assert e.classes, f"mode {mode_id}: engine {e.path} declares no classes"
+    for cls_name in ("truck", "sack", "box"):
+        dp = cfg.detection_params_for(cls_name)
+        assert 0.0 < dp.conf <= 1.0
+        assert 0.0 < dp.iou <= 1.0
+        assert dp.min_bbox_area >= 0
+
+
+def test_mode_preset_only_filters_and_engines(repo_config_path):
+    """Modes must not carry per-class conf/iou — those live in detection_params."""
+    with open(repo_config_path) as f:
+        raw = yaml.safe_load(f)
+    for mode_id, mode in raw["models"]["modes"].items():
+        assert "conf" not in mode, f"mode {mode_id}: conf belongs in detection_params"
+        assert "iou" not in mode, f"mode {mode_id}: iou belongs in detection_params"
+        assert "min_bbox_area" not in mode, f"mode {mode_id}"
+
+
+def test_resolve_active_mode_precedence(repo_config_path, monkeypatch):
+    cfg = load_config(repo_config_path)
+    monkeypatch.delenv("MODEL_MODE", raising=False)
+    assert resolve_active_mode(None, cfg) == "C"
+    assert resolve_active_mode("d", cfg) == "D"
+    with pytest.warns(UserWarning):  # unknown -> fallback to active
+        assert resolve_active_mode("Z", cfg) == "C"
+    monkeypatch.setenv("MODEL_MODE", "B")
+    with pytest.warns(DeprecationWarning):  # env still honoured, deprecated
+        assert resolve_active_mode(None, cfg) == "B"
+
+
+def test_missing_file_falls_back_with_warning(tmp_path, monkeypatch):
+    monkeypatch.delenv("MODEL_MODE", raising=False)
+    with pytest.warns(UserWarning, match="not found"):
+        cfg = load_config(tmp_path / "nope.yaml")
+    assert cfg.models.active_mode == "C"
+    assert cfg.stream.inference_stride == 2
+
+
+def test_set_active_mode_roundtrip_and_validation(tmp_path, repo_config_path):
+    import shutil
+
+    dst = tmp_path / "config.yaml"
+    shutil.copy(repo_config_path, dst)
+    assert set_active_mode(dst, "d") == "D"
+    assert load_config(dst).models.active_mode == "D"
+    text = dst.read_text()
+    assert 'active_mode: "D"' in text
+    assert "# config.yaml" in text  # comments preserved (no yaml.dump reformat)
+    with pytest.raises(ValueError, match="Invalid model mode"):
+        set_active_mode(dst, "Z")
+    assert load_config(dst).models.active_mode == "D"  # untouched on failure
+
+
+def test_future_mode_extensible_without_code(tmp_path, repo_config_path):
+    """Adding mode E is a YAML-only change: loader accepts it, no code edits."""
+    import shutil
+
+    dst = tmp_path / "config.yaml"
+    shutil.copy(repo_config_path, dst)
+    with open(dst) as f:
+        raw = yaml.safe_load(f)
+    raw["models"]["modes"]["E"] = {
+        "description": "hypothetical future preset",
+        "engines": [{"path": "combined", "classes": ["truck", "sack"]}],
+        "class_filters": {"truck": ["truck"], "sack": ["sack"], "box": []},
+    }
+    with open(dst, "w") as f:
+        yaml.safe_dump(raw, f)
+    cfg = load_config(dst)
+    assert resolve_active_mode("E", cfg) == "E"
+    assert set_active_mode(dst, "E") == "E"
+
+
+def test_legacy_batch_mode_check(tmp_path, repo_config_path):
+    cfg = load_config(repo_config_path)
+    legacy = tmp_path / "batch_mode.json"
+    legacy.write_text(json.dumps({"mode": "auto", "model_mode": "B"}))
+    msg = check_legacy_batch_mode(cfg, legacy)
+    assert msg is not None and "'B'" in msg and "'C'" in msg
+    legacy.write_text(json.dumps({"mode": "auto", "model_mode": "C"}))
+    assert check_legacy_batch_mode(cfg, legacy) is None
+    assert check_legacy_batch_mode(cfg, tmp_path / "missing.json") is None
+
+
+def test_zone_polygons_and_legacy_knob_warning(tmp_path):
+    zf = tmp_path / "zones.json"
+    zf.write_text(json.dumps({
+        "palet": [[0, 0]], "truck": [[1, 1]], "counting": [[2, 2]],
+        "left_limit": 0.27, "right_limit": 0.72,
+        "duplicate_circle_radius": 30,  # legacy knob -> ignored + warned
+    }))
+    with pytest.warns(UserWarning, match="legacy knob"):
+        zones = read_zone_polygons(zf)
+    assert zones["palet"] == [[0, 0]]
+    assert zones["left_limit"] == 0.27  # geometry stays in zones.json