feat: 新增本机 CPU checker

- 新增 type: cpu checker，基于 os.cpus() 两次快照计算 CPU 使用率
- 配置项：sampleDuration（默认 1s）、includePerCore（默认 false）
- expect 字段：usagePercent、idlePercent、maxCoreUsagePercent、minCoreUsagePercent、durationMs
- idlePercent 与 usagePercent 互补恒等于 100，百分比范围 0-100
- logicalCoreCount 仅输出到 observation，不作为 expect 字段
- 不暴露 userPercent / systemPercent
- 语义校验禁止 sampleDuration >= timeout
- 支持 AbortSignal 超时取消
- 完整测试覆盖：schema、validate、normalize、resolve、calculate、execute、expect、config-loader
- 新增用户文档 docs/user/checkers/cpu.md
- 更新 checker 索引、配置类型列表、示例配置和 schema

tests/server/checker/runner/cpu/calculate.test.ts

@@ -0,0 +1,112 @@
+import { describe, expect, test } from "bun:test";
+
+import type { CpuCoreSnapshot } from "../../../../../src/server/checker/runner/cpu/types";
+
+import { calculateCpuStats } from "../../../../../src/server/checker/runner/cpu/calculate";
+
+function makeCore(user: number, nice: number, sys: number, idle: number, irq: number): CpuCoreSnapshot {
+  return { times: { idle, irq, nice, sys, user } };
+}
+
+describe("calculateCpuStats", () => {
+  test("单核心完全空闲", () => {
+    const before = [makeCore(0, 0, 0, 100, 0)];
+    const after = [makeCore(0, 0, 0, 200, 0)];
+    const stats = calculateCpuStats(before, after);
+    expect(stats.usagePercent).toBe(0);
+    expect(stats.idlePercent).toBe(100);
+    expect(stats.maxCoreUsagePercent).toBe(0);
+    expect(stats.minCoreUsagePercent).toBe(0);
+    expect(stats.logicalCoreCount).toBe(1);
+  });
+
+  test("单核心完全忙碌（idle 不变）", () => {
+    const before = [makeCore(100, 0, 0, 100, 0)];
+    const after = [makeCore(200, 0, 0, 100, 0)];
+    // idle delta = 0, total delta = 100
+    // idlePercent = 0, usagePercent = 100
+    const stats = calculateCpuStats(before, after);
+    expect(stats.usagePercent).toBe(100);
+    expect(stats.idlePercent).toBe(0);
+  });
+
+  test("单核心部分使用", () => {
+    const before = [makeCore(100, 0, 0, 900, 0)];
+    const after = [makeCore(150, 0, 0, 950, 0)];
+    // idle delta = 50, total delta = 100
+    // idlePercent = 50, usagePercent = 50
+    const stats = calculateCpuStats(before, after);
+    expect(stats.usagePercent).toBe(50);
+    expect(stats.idlePercent).toBe(50);
+  });
+
+  test("多核心加权平均", () => {
+    // 核心 0: idle delta = 200, total delta = 1000 -> 80% usage
+    // 核心 1: idle delta = 800, total delta = 1000 -> 20% usage
+    const before = [makeCore(0, 0, 0, 1000, 0), makeCore(0, 0, 0, 1000, 0)];
+    const after = [makeCore(800, 0, 0, 1200, 0), makeCore(200, 0, 0, 1800, 0)];
+    const stats = calculateCpuStats(before, after);
+    // 总 idle = 200+800=1000, 总 delta = 1000+1000=2000
+    // idlePercent = 1000/2000*100 = 50
+    // usagePercent = 100 - 50 = 50
+    expect(stats.idlePercent).toBe(50);
+    expect(stats.usagePercent).toBe(50);
+    expect(stats.maxCoreUsagePercent).toBe(80);
+    expect(stats.minCoreUsagePercent).toBe(20);
+    expect(stats.logicalCoreCount).toBe(2);
+    expect(stats.perCoreUsagePercent).toEqual([80, 20]);
+  });
+
+  test("四核心各不相同", () => {
+    const bf = [
+      makeCore(1000, 0, 0, 9000, 0), // core 0 baseline
+      makeCore(1000, 0, 0, 9000, 0), // core 1
+      makeCore(1000, 0, 0, 9000, 0), // core 2
+      makeCore(1000, 0, 0, 9000, 0), // core 3
+    ];
+    const af = [
+      makeCore(1900, 0, 0, 9100, 0), // delta: user=900, idle=100, total=1000 -> 90% usage, 10% idle
+      makeCore(1500, 0, 0, 9500, 0), // delta: user=500, idle=500, total=1000 -> 50% usage
+      makeCore(1200, 0, 0, 9800, 0), // delta: user=200, idle=800, total=1000 -> 20% usage
+      makeCore(1010, 0, 0, 9990, 0), // delta: user=10, idle=990, total=1000 -> 1% usage
+    ];
+    const stats = calculateCpuStats(bf, af);
+    // 总 idle = 100+500+800+990 = 2390, 总 delta = 4000
+    // idlePercent = 2390/4000*100 = 59.75 -> 59.8
+    expect(stats.idlePercent).toBe(59.8);
+    expect(stats.usagePercent).toBe(40.2);
+    expect(stats.maxCoreUsagePercent).toBe(90);
+    expect(stats.minCoreUsagePercent).toBe(1);
+    expect(stats.perCoreUsagePercent).toEqual([90, 50, 20, 1]);
+    expect(stats.logicalCoreCount).toBe(4);
+  });
+
+  test("delta 为 0 时返回 0", () => {
+    const before = [makeCore(100, 0, 0, 100, 0)];
+    const after = [makeCore(100, 0, 0, 100, 0)];
+    const stats = calculateCpuStats(before, after);
+    expect(stats.usagePercent).toBe(0);
+    expect(stats.idlePercent).toBe(0);
+  });
+
+  test("保留 1 位小数", () => {
+    // 总 idle = 333, 总 delta = 1000 -> idlePercent = 33.3
+    const before = [makeCore(0, 0, 0, 1000, 0)];
+    const after = [makeCore(667, 0, 0, 1333, 0)];
+    const stats = calculateCpuStats(before, after);
+    // idle delta = 333, total delta = 1000
+    expect(stats.idlePercent).toBe(33.3);
+    expect(stats.usagePercent).toBe(66.7);
+  });
+
+  test("nice 和 irq 计入 total 但不影响 idle", () => {
+    const bf = [makeCore(0, 0, 0, 0, 0)];
+    const af = [makeCore(300, 100, 100, 400, 100)];
+    // total delta = 300+100+100+400+100 = 1000
+    // idle delta = 400
+    // idlePercent = 400/1000*100 = 40
+    const stats = calculateCpuStats(bf, af);
+    expect(stats.idlePercent).toBe(40);
+    expect(stats.usagePercent).toBe(60);
+  });
+});