feat(prompt): 重新注册 bash，把"不要用 bash 搜索"写进工具描述

真实会话里模型仍习惯性先调 bash grep，被拒后才改用 grep 工具；系统提示词里已有 4 处
提醒，但模型下调用决定时看的是工具 schema 描述，而 Pi 内置 bash 描述对此只字未提。

- 新增 extensions/bash-override.ts：用 Pi 的 createBashToolDefinition 重新注册 bash，
  执行、输出结构与 codemode 说明完全沿用上游；shellPath/commandPrefix 按 ctx.cwd
  经 SettingsManager 惰性解析，与内置一致
- tools.jsonc 新增 descriptionAppend 字段，由 prompt-guard 注册时拼接到上游描述后
- bash 增加命令→工具对照规则（grep -n / grep -rl / find -name），并提示
  文件清单用 $(git ls-files) 传参、不要接 xargs（会触发权限审核）

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

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

config/prompt/tools.jsonc

@@ -2,17 +2,26 @@
   // Bundle-authoritative tool guidance, owned by extensions/system-prompt.ts.
   //
   // Every tool the bundle can expose must have an entry. Per field:
-  //   "snippet"     — replaces the tool's one-line <tools> entry (null hides it)
-  //   "guidelines"  — replaces the tool's <rules> lines
-  //   "description" — replaces the tool description at registration; only
-  //                   applied to third-party tools loaded through a bundle
-  //                   adapter (in-repo tools edit their own source instead)
+  //   "snippet"           — replaces the tool's one-line <tools> entry (null hides it)
+  //   "guidelines"        — replaces the tool's <rules> lines
+  //   "description"       — replaces the tool description at registration
+  //   "descriptionAppend" — appended to the description at registration (on top
+  //                         of "description" when both are set)
+  // "description"/"descriptionAppend" only apply to tools registered through a
+  // bundle adapter (prompt-guard), which includes the bash override and the
+  // third-party wrappers; other in-repo tools edit their own source instead.
   // An absent field keeps the upstream text. "inherit": true means the
   // upstream text was reviewed against this bundle and is kept as-is.
   "version": 1,
   "tools": {
     "bash": {
-      "snippet": "Run shell commands for builds, tests, git, package scripts, and other programs; search files with the find/grep tools, not bash"
+      "snippet": "Run shell commands for builds, tests, git, package scripts, and other programs; search files with the find/grep tools, not bash",
+      "descriptionAppend": "Not for searching files: use the grep tool for file contents and the find tool for paths (e.g. `grep -n X src/*.ts` → grep {pattern: \"X\", path: \"src/*.ts\"}); grep, rg, find, fd, and git grep are denied here. When a program needs many files, pass $(git ls-files '<glob>') as arguments instead of piping into xargs, which triggers a permission review.",
+      "guidelines": [
+        "You can inspect PI_* environment variables for current model and session details.",
+        "Search commands are denied in bash; call the tools instead: `grep -n X src/*.ts` → grep {pattern: \"X\", path: \"src/*.ts\"}; `grep -rl X src` → grep {pattern: \"X\", path: \"src/\"} and take the file names; `find . -name '*.ts'` → find {pattern: \"\", path: \"**/*.ts\"}.",
+        "When a program needs many files (wc, node, tsc), pass $(git ls-files '<glob>') as arguments; piping into xargs triggers a permission review."
+      ]
     },
     "read": { "inherit": true },
     "edit": {