step 2: add thread safe state commands and cache model

src/dpg_map/overlays.py

@@ -1 +1,72 @@
 """Logical overlay models."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from dataclasses import dataclass, field
+from typing import Any
+
+from .types import Color, LatLon, Tag
+
+
+@dataclass(slots=True)
+class Overlay:
+    """Base logical overlay state."""
+
+    tag: Tag
+    map_tag: Tag
+    layer: str
+    show: bool = True
+    user_data: Any = None
+    revision: int = 0
+
+    def touch(self) -> None:
+        """Mark this overlay as changed."""
+
+        self.revision += 1
+
+
+@dataclass(slots=True)
+class MarkerOverlay(Overlay):
+    """Logical marker overlay."""
+
+    lat: float = 0.0
+    lon: float = 0.0
+    label: str | None = None
+    color: Color = (255, 80, 80, 255)
+    radius: float = 5.0
+    show_label: bool = False
+    callback: Callable[..., Any] | None = None
+
+
+@dataclass(slots=True)
+class PolylineOverlay(Overlay):
+    """Logical polyline overlay."""
+
+    points: tuple[LatLon, ...] = ()
+    color: Color = (80, 180, 255, 255)
+    thickness: float = 2.0
+    closed: bool = False
+    simplify: bool = True
+
+
+@dataclass(slots=True)
+class TrajectoryOverlay(Overlay):
+    """Logical trajectory overlay."""
+
+    points: tuple[LatLon, ...] = ()
+    timestamps: tuple[float, ...] | None = None
+    color: Color = (255, 180, 60, 255)
+    thickness: float = 2.0
+    show_points: bool = False
+    point_stride: int = 1
+
+
+@dataclass(slots=True)
+class LayerState:
+    """Logical layer visibility and ordering state."""
+
+    name: str
+    z_index: int = 0
+    show: bool = True
+    overlay_tags: set[Tag] = field(default_factory=set)