refactor(hub): Vercel AI SDK → Claude Code SDK

用 @anthropic-ai/claude-agent-sdk 的 query() 替换 Vercel AI SDK 的
streamText。SDK 自带 Read/Write/Bash/Glob/Grep 工具——read_file/
write_file/list_files/cph_check/cph_build 全部不需要了,Bash 跑
cph 直接。

UX 同时改成 workbuddy 风格:
- 收到 @bot → 表情回复(👍)确认收到,不发'已开始处理'
- agent 回复作为文本流式发送(text-as-card patch,markdown 渲染)
- 超长自动续发新消息,不截断
- 完成/出错不再额外发状态消息
- 去掉卡片(model选择器/取消按钮)

ADR-0017 更新:放弃 provider-agnostic,Claude Code SDK 是 Anthropic
专有。换来:compaction、工具审批、partial message 流式、成熟 agent
loop。

tsc rc=0。旧文件(workspace.ts/cph.ts/provider.ts/tools.ts)暂留,
下个 commit 清理。

hub/src/agent/models.ts

@@ -32,13 +32,13 @@ export interface RoleEntry {
    * run's messages only at session start (resume reads it from the transcript,
    * see runner.ts). `undefined` ⇒ no system prompt (bare run).
    */
-  readonly systemPrompt: string | undefined;
+  readonly systemPrompt?: string | undefined;
   /**
    * Tool names this role may use (whitelist). `undefined` ⇒ the full registered
    * set (back-compat / unrestricted roles). An empty array ⇒ no tools at all.
    * Names not present in the registry are silently dropped at run setup.
    */
-  readonly tools: readonly string[] | undefined;
+  readonly tools?: readonly string[] | undefined;
 }
 
 /** A model the admin has enabled for use by the Hub. */