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>

tests/system-prompt.test.ts

@@ -21,6 +21,7 @@ import {
 	stripJsoncComments,
 	validateRoutingConfig,
 	validateSectionsConfig,
+	validateToolCatalog,
 	type MutablePromptOptions,
 	type RoutingRule,
 } from "../extensions/system-prompt-config.ts";
@@ -28,7 +29,7 @@ import systemPromptExtension, {
 	createSystemPromptComposer,
 	getSystemPromptDumpPath,
 } from "../extensions/system-prompt.ts";
-import { guardExtensionApi } from "../extensions/prompt-guard.ts";
+import { catalogDescription, guardExtensionApi } from "../extensions/prompt-guard.ts";
 import { BUNDLE_GROUP_DEFINITIONS } from "../pi-tool-search/extensions/bundle-groups.ts";
 import { BUNDLE_TOOL_SEARCH_DEFAULTS } from "../pi-tool-search/extensions/config.ts";
 
@@ -93,6 +94,20 @@ test("routing scope validation: main/subagent accepted, other values rejected",
 	);
 });
 
+test("tools.jsonc validation: descriptionAppend accepted as a string, rejected otherwise", () => {
+	assert.doesNotThrow(() =>
+		validateToolCatalog({ version: 1, tools: { bash: { descriptionAppend: "extra" } } }),
+	);
+	assert.throws(
+		() => validateToolCatalog({ version: 1, tools: { bash: { descriptionAppend: 5 } } }),
+		/descriptionAppend must be a string/,
+	);
+	assert.throws(
+		() => validateToolCatalog({ version: 1, tools: { bash: { descriptionAppend: true } } }),
+		/descriptionAppend must be a string/,
+	);
+});
+
 test("sections.jsonc validation: subagentExclude defaults to [] and rejects bad shapes", () => {
 	assert.deepEqual(validateSectionsConfig({ version: 1, order: ["tool_routing"] }), {
 		version: 1,
@@ -608,7 +623,38 @@ test("prompt guard applies catalog description overrides at registration", () =>
 	const override = loadToolCatalog().tools.edit;
 	assert.ok(override && !("inherit" in override) && typeof override.description === "string");
 	assert.equal(tools[0].description, override.description);
-	assert.equal(tools[1].description, "upstream grep", "inherit entries keep the upstream description");
+	assert.equal(tools[1].description, "upstream grep", "entries without description fields keep the upstream description");
+});
+
+test("prompt guard appends the catalog descriptionAppend to the upstream description", () => {
+	const { pi, tools } = makeRecordingPi();
+	const guarded = guardExtensionApi(pi as unknown as ExtensionAPI);
+
+	guarded.registerTool({ name: "bash", description: "upstream bash" } as never);
+	guarded.registerTool({ name: "read", description: "upstream read" } as never);
+
+	const bashEntry = loadToolCatalog().tools.bash;
+	assert.ok(bashEntry && !("inherit" in bashEntry) && typeof bashEntry.descriptionAppend === "string");
+	assert.equal(tools[0].description, `upstream bash\n\n${bashEntry.descriptionAppend}`);
+	assert.equal(tools[1].description, "upstream read", "inherit entries keep the upstream description");
+});
+
+test("catalogDescription composes override, append, and inherit", () => {
+	assert.equal(
+		catalogDescription("upstream", { description: "override", descriptionAppend: "append" }),
+		"override\n\nappend",
+		"an append sits on top of the description override when both are set",
+	);
+	assert.equal(
+		catalogDescription("upstream  \n", { descriptionAppend: "append" }),
+		"upstream\n\nappend",
+		"trailing whitespace on the base is trimmed before the blank line",
+	);
+	assert.equal(
+		catalogDescription("upstream", { inherit: true }),
+		"upstream",
+		"inherit entries are untouched",
+	);
 });
 
 test("prompt guard strips a returned systemPrompt but keeps other fields", async () => {