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-permission-system/src/handlers/before-agent-start.ts

@@ -4,17 +4,30 @@ import type {
 } from "@earendil-works/pi-coding-agent";
 import type { PermissionResolver } from "#src/permission-resolver";
 import type { PermissionSession } from "#src/permission-session";
-import { resolveSkillPromptEntries } from "#src/skill-prompt-sanitizer";
+import {
+  resolveSkillPromptEntries,
+  resolveStructuredSkillEntries,
+  type StructuredSkillLike,
+} from "#src/skill-prompt-sanitizer";
 
 /** Minimal subset of BeforeAgentStartEvent used by this handler. */
 interface BeforeAgentStartPayload {
   systemPrompt: string;
+  systemPromptOptions?: {
+    skills?: StructuredSkillLike[] | unknown;
+  };
 }
 
 /**
  * Prepares permission state before an agent turn without changing Pi's active
  * tool set. Tool Search is the bundle's sole active-tool controller; this
  * handler only refreshes permission state and sanitizes denied skill entries.
+ *
+ * Under the bundle's single system-prompt owner (extensions/system-prompt.ts)
+ * no handler may return `systemPrompt`: when the event carries the structured
+ * `systemPromptOptions.skills` array the denied entries are filtered out of it
+ * directly. The rendered-text rewrite remains only as a fallback for hosts
+ * that do not expose structured skills.
  */
 export class AgentPrepHandler {
   constructor(
@@ -36,6 +49,20 @@ export class AgentPrepHandler {
     this.session.refreshConfig(ctx, ctx.isProjectTrusted());
 
     const agentName = this.session.resolveAgentName(ctx, event.systemPrompt);
+
+    const options = event.systemPromptOptions;
+    if (options && Array.isArray(options.skills)) {
+      const structured = resolveStructuredSkillEntries(
+        options.skills,
+        this.resolver,
+        agentName,
+        this.session.getPathNormalizer(),
+      );
+      options.skills = structured.skills;
+      this.session.setActiveSkillEntries(structured.entries);
+      return {};
+    }
+
     const skillPromptResult = resolveSkillPromptEntries(
       event.systemPrompt,
       this.resolver,

pi-permission-system/src/skill-prompt-sanitizer.ts

@@ -251,6 +251,82 @@ export function resolveSkillPromptEntries(
   };
 }
 
+/**
+ * Minimal structural shape of Pi's `Skill` as carried on
+ * `systemPromptOptions.skills` (Pi 1.x). Fields not listed here are passed
+ * through untouched.
+ */
+export interface StructuredSkillLike {
+  name?: unknown;
+  description?: unknown;
+  filePath?: unknown;
+  baseDir?: unknown;
+  disableModelInvocation?: unknown;
+}
+
+/**
+ * Structured counterpart of `resolveSkillPromptEntries`: Pi 1.x exposes the
+ * loaded skills as objects on `systemPromptOptions.skills`, so denied skills
+ * are filtered out of that array instead of being cut from rendered text.
+ * Skills that Pi itself hides from the prompt (`disableModelInvocation`) stay
+ * in the array but are excluded from the active-entry list, matching the text
+ * path where they never appeared in `<available_skills>`.
+ */
+export function resolveStructuredSkillEntries(
+  skills: readonly StructuredSkillLike[],
+  permissionManager: SkillPermissionChecker,
+  agentName: string | null,
+  normalizer: PathNormalizer,
+): { skills: StructuredSkillLike[]; entries: SkillPromptEntry[] } {
+  const permissionCache = new Map<string, PermissionState>();
+  const visibleSkills: StructuredSkillLike[] = [];
+  const entries: SkillPromptEntry[] = [];
+
+  for (const skill of skills) {
+    const name = typeof skill?.name === "string" ? skill.name : "";
+    if (!name) {
+      visibleSkills.push(skill);
+      continue;
+    }
+    const state = resolvePermissionState(
+      name,
+      permissionManager,
+      agentName,
+      permissionCache,
+    );
+    if (state === "deny") {
+      continue;
+    }
+    visibleSkills.push(skill);
+    if (skill.disableModelInvocation === true) {
+      continue;
+    }
+    const location =
+      typeof skill.filePath === "string" && skill.filePath
+        ? skill.filePath
+        : typeof skill.baseDir === "string"
+          ? skill.baseDir
+          : "";
+    const baseDir =
+      typeof skill.baseDir === "string" && skill.baseDir
+        ? skill.baseDir
+        : location
+          ? dirname(location)
+          : "";
+    entries.push({
+      name,
+      description:
+        typeof skill.description === "string" ? skill.description : "",
+      location,
+      state,
+      normalizedLocation: normalizer.comparableValue(location),
+      normalizedBaseDir: normalizer.comparableValue(baseDir),
+    });
+  }
+
+  return { skills: visibleSkills, entries };
+}
+
 export function findSkillPathMatch(
   normalizedPath: string,
   entries: readonly SkillPromptEntry[],