feat(cli): Add tttk check validator

Statically validate a directory of tttk documents and report structured diagnostics with file/line positions, exit codes, and --json output. Checks cover code-block roles, unresolved content references, tag blocks, element names, links, anchors, and assets. Runs over the same content registry as the app.

src/cli/index.ts

@@ -2,6 +2,7 @@
 import { Command } from "commander";
 import { serveCommand } from "./commands/serve.js";
 import { compileCommand } from "./commands/compile.js";
+import { checkCommand } from "./commands/check.js";
 import { mcpCommand } from "./commands/mcp.js";
 import type { ServeOptions, CompileOptions } from "./types.js";
 
@@ -22,6 +23,16 @@ program
   .option("--host <host>", "主机地址", "0.0.0.0")
   .action(serveCommand);
 
+program
+  .command("check")
+  .alias("lint")
+  .description("校验目录内的 tttk 文档，输出结构化诊断")
+  .argument("[dir]", "要校验的目录", ".")
+  .option("--json", "以 JSON 输出诊断", false)
+  .option("--strict", "将警告视为错误", false)
+  .option("--quiet", "只报告错误", false)
+  .action(checkCommand);
+
 program
   .command("compile")
   .description("[未实现] 存根命令：不会生成任何输出。预览内容请使用 tttk serve")