feat: 重构配置校验为 TypeBox + Ajv + semantic validator，严格禁止未知字段

- 新增 config-contract 模块（TypeBox fragments、Ajv 契约校验、ConfigValidationIssue）
- CheckerDefinition 扩展为含 configKey、schemas、validate 的完整插件接口
- HTTP/Command 各自维护 contract.ts + validate.ts，校验从 resolve 中分离
- resolve 不再承担校验，只做默认值合并和路径/单位解析
- config-loader 流程: unknown → RawProbeConfig → ValidatedProbeConfig → ResolvedConfig
- 导出 probe-config.schema.json，新增 schema/schema:check 脚本
- 更新 DEVELOPMENT.md 新增 1.7 开发新 Checker 完整指引
- 同步更新 4 个 main specs（probe-config、command-checker、expect-body-checkers、checker-runner-abstraction）

src/server/checker/config-contract/schema.ts

@@ -0,0 +1,89 @@
+import type { TSchema } from "@sinclair/typebox";
+
+import { Type } from "@sinclair/typebox";
+
+import type { CheckerDefinition } from "../runner/types";
+
+import { durationSchema } from "./fragments";
+
+export function createExternalProbeConfigSchema(checkers: CheckerDefinition[]): Record<string, unknown> {
+  return {
+    ...cloneSchema(createProbeConfigSchema(checkers, true)),
+    $id: "https://dial.local/probe-config.schema.json",
+    $schema: "http://json-schema.org/draft-07/schema#",
+    definitions: {},
+  };
+}
+
+export function createProbeConfigSchema(checkers: CheckerDefinition[], external = false): TSchema {
+  return Type.Object(
+    {
+      defaults: Type.Optional(createDefaultsSchema(checkers)),
+      runtime: Type.Optional(
+        Type.Object(
+          { maxConcurrentChecks: Type.Optional(Type.Integer({ minimum: 1 })) },
+          { additionalProperties: false },
+        ),
+      ),
+      server: Type.Optional(
+        Type.Object(
+          {
+            dataDir: Type.Optional(Type.String()),
+            host: Type.Optional(Type.String()),
+            port: Type.Optional(Type.Integer({ maximum: 65535, minimum: 0 })),
+          },
+          { additionalProperties: false },
+        ),
+      ),
+      targets: Type.Array(external ? createExternalTargetSchema(checkers) : createBaseTargetSchema(checkers), {
+        minItems: 1,
+      }),
+    },
+    { additionalProperties: false },
+  );
+}
+
+export function createTargetSchema(checker: CheckerDefinition): TSchema {
+  const properties: Record<string, TSchema> = {
+    expect: Type.Optional(checker.schemas.expect),
+    group: Type.Optional(Type.String()),
+    interval: Type.Optional(durationSchema),
+    name: Type.String({ minLength: 1 }),
+    timeout: Type.Optional(durationSchema),
+    type: Type.Literal(checker.type),
+  };
+  properties[checker.configKey] = checker.schemas.config;
+  return Type.Object(properties, { additionalProperties: false });
+}
+
+function cloneSchema(schema: TSchema): Record<string, unknown> {
+  return JSON.parse(JSON.stringify(schema)) as Record<string, unknown>;
+}
+
+function createBaseTargetSchema(checkers: CheckerDefinition[]): TSchema {
+  return Type.Object(
+    {
+      group: Type.Optional(Type.String()),
+      interval: Type.Optional(durationSchema),
+      name: Type.String({ minLength: 1 }),
+      timeout: Type.Optional(durationSchema),
+      type: Type.Union(checkers.map((checker) => Type.Literal(checker.type)) as unknown as [TSchema, ...TSchema[]]),
+    },
+    { additionalProperties: true },
+  );
+}
+
+function createDefaultsSchema(checkers: CheckerDefinition[]): TSchema {
+  const properties: Record<string, TSchema> = {
+    interval: Type.Optional(durationSchema),
+    timeout: Type.Optional(durationSchema),
+  };
+  for (const checker of checkers) {
+    properties[checker.configKey] = Type.Optional(checker.schemas.defaults);
+  }
+  return Type.Object(properties, { additionalProperties: false });
+}
+
+function createExternalTargetSchema(checkers: CheckerDefinition[]): TSchema {
+  return Type.Union(checkers.map((checker) => createTargetSchema(checker)) as [TSchema, ...TSchema[]]);
+}