feat: 系统提示词改为单一入口统一管理

多个扩展各自整段改写系统提示词并按加载顺序接力，任一扩展定死提示词后
其余只能做字符串手术，且各上游的工具说明与组合包实际工具格局冲突。

- 新增 extensions/system-prompt.ts 作为唯一出口（加载列表最后），按
  config/prompt/（preamble.md、tools.jsonc、routing.jsonc、sections.jsonc）
  组合开场白、工具简介/规则与 <tool_routing> 分区；替代原封面与
  tool-routing 扩展，/dump-system-prompt 输出最终提示词。
- pi-chrome、pi-ssh、pi-hermes-memory 改为写命名分区，pi-rtk-optimizer
  改写 promptGuidelines，pi-permission-system 直接过滤结构化 skills，
  均不再返回 systemPrompt；pi-chrome 未授权时不再每轮冻结提示词。
- 新增 prompt-guard 代理加载第三方扩展（Hashline、FFF、LSP、
  context-mode）：拦截直接改写提示词并按目录覆盖工具说明；context-mode
  去掉与组合包路由冲突的锚点段，保留记忆与恢复快照。
- 消除冲突：bash 简介不再建议 grep/find；Hashline edit 不再称可用 grep
  锚点、不再介绍已关闭的 replace_text；context-mode 读写/网页路由提示。
- 守门测试：工具目录覆盖率、禁用用法检查、context-mode 上游原文锁定；
  AGENTS.md 新增「系统提示词单一所有权」。

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

pi-ssh/index.ts

@@ -355,8 +355,10 @@ export default function piSshExtension(pi: ExtensionAPI): void {
 
   pi.on("before_agent_start", async (event) => {
     if (!connection) return;
+    // Contribute structurally via a named section: the bundle's single
+    // system-prompt owner (extensions/system-prompt.ts) composes the final
+    // prompt; extensions must not return `systemPrompt` themselves.
     const guidance =
-      `\n\n# Remote SSH connection\n\n` +
       `An SSH2 connection to configured host ${connection.remote} on port ${connection.port} is active. ` +
       `The default read/write/edit/bash/find/grep tools act on the LOCAL machine. ` +
       `Use ssh_cd, ssh_read, ssh_write, ssh_edit, ssh_find, ssh_grep, and ssh_bash for explicit remote operations. ` +
@@ -364,6 +366,10 @@ export default function piSshExtension(pi: ExtensionAPI): void {
       `Remote operations are rooted at ${connection.remoteCwd}; relative paths resolve against that directory. ` +
       `For a persistent workspace change, call ssh_cd as a separate step and wait for its successful result before issuing dependent remote tool calls. ` +
       `Each ssh_bash call starts a fresh non-interactive shell, so use command-local cd only for an intentionally temporary change; cd, exports, aliases, and other shell state inside one command do not persist to the next call.`;
-    return { systemPrompt: `${event.systemPrompt}${guidance}` };
+    const promptOptions = event.systemPromptOptions as unknown as
+      | { sections?: Record<string, string> }
+      | undefined;
+    if (!promptOptions) return; // hosts without structured options just skip the section
+    (promptOptions.sections ??= {}).remote_ssh = guidance;
   });
 }