refactor(arch): redesign the code structure

src/mcm26b/coverage/__init__.py

@@ -0,0 +1,56 @@
+"""P4 全域覆盖：49 点网格与逐频道覆盖记录。
+
+覆盖基线（推导见 docs/B题建模分析与实施计划.md §4）：
+S = {(700i, 700j) : i, j ∈ [-3,3]}，|S| = 49，覆盖 [-2100,2100]² ⊇ Ω，
+且允许访问目标圆域外（边界朝外发射的定向源不漏）。
+单元内任意点到 4 顶点距离 <= 700·√2 ≈ 989.95 <= 1000 <= 最小接收半径。
+
+验收标准：
+- "路过某点"不算"测过某频道"：必须按 (频道, 点) 二维记录；
+- 已清除/已定位频道可跳过剩余点，但跳过原因必须留痕；
+- 自适应跳点（P6）必须保留逐频道覆盖证据，否则不得启用。
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+
+from ..config import ProblemConfig, Vec2
+
+
+def coverage_points(config: ProblemConfig = ProblemConfig()) -> list[Vec2]:
+    """49 点覆盖网格生成（纯几何，可独立测试）。"""
+    step = config.search.grid_step_m
+    half = config.search.grid_half_cells
+    return [(step * i, step * j)
+            for j in range(half, -half - 1, -1)
+            for i in range(-half, half + 1)]
+
+
+@dataclass
+class CoverageLedger:
+    """逐频道覆盖账本：(频道, 网格点) -> 是否已测。"""
+
+    config: ProblemConfig = field(default_factory=ProblemConfig)
+    points: list[Vec2] = field(default_factory=lambda: coverage_points())
+    measured: set = field(default_factory=set)          # {(channel, point_index)}
+    skipped: dict = field(default_factory=dict)         # channel -> 原因
+
+    def mark_measured(self, channel: int, point_index: int) -> None:
+        self.measured.add((channel, point_index))
+
+    def measured_at(self, channel: int, point_index: int) -> bool:
+        return (channel, point_index) in self.measured
+
+    def skip_channel(self, channel: int, reason: str) -> None:
+        """记录整频道跳过原因（如 already_cleared / located_pending_clear）。"""
+        self.skipped[channel] = reason
+
+    def pending_points(self, channel: int) -> list[int]:
+        """该频道尚未测量的网格点下标。扫描调度策略未实现（P4）。"""
+        return [index for index in range(len(self.points))
+                if not self.measured_at(channel, index)]
+
+    def coverage_complete(self, channel: int) -> bool:
+        """该频道覆盖是否完成（含显式跳过）。"""
+        return channel in self.skipped or not self.pending_points(channel)