feat(prompt): 搜索引导改为意图→工具的正向指引，multi_grep 按上游保持关闭

真实会话中模型仍用 bash grep -o | sort -u 做抽取，被拒后直接放弃核对；
原提示词只说"不要"，没告诉它抽取/计数、给程序传文件清单、过滤命令输出时该用什么。

- routing：按已知信息选 grep/find（多变体用 grep 正则 alternation），
  codemode + tools.grep 做聚合，bash 文件清单用 git ls-files，
  overflow_query 过滤输出，被拒后改用替代方案继续
- 权限策略：rg/grep/git grep/find/fd 的 deny 附带指向替代工具的 reason
- tools.jsonc：grep/find 新 snippet，补上 codegraph_explore snippet
- FFF 上游标注 multi_grep 有害：wrapper 删除 PI_FFF_MULTIGREP，清理全部引用
- JSONC 测试改用字符串感知的注释剥离（reason 中含 'src/**/*.ts'）

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

config/pi-permission-policy.jsonc

@@ -37,7 +37,6 @@
     "edit": "allow",
     "grep": "allow",
     "find": "allow",
-    "multi_grep": "allow",
     "ls": "allow",
     "codegraph_explore": "allow",
     "lsp_diagnostics": "allow",
@@ -103,10 +102,10 @@
     },
     "bash": {
       "*": "allow",
-      "rg*": "deny",
-      "grep*": "deny",
-      "find*": "deny",
-      "fd*": "deny",
+      "rg*": { "action": "deny", "reason": "Bash content search is disabled. Locally use the grep tool (pattern + path/exclude; regex alternation for several names); to extract/dedupe/count matches, call tools.grep in codemode and process in JS; to filter command output, use overflow_query on the stored result. Over SSH use ssh_grep." },
+      "grep*": { "action": "deny", "reason": "Bash content search is disabled. Locally use the grep tool (pattern + path/exclude; regex alternation for several names); to extract/dedupe/count matches, call tools.grep in codemode and process in JS; to filter command output, use overflow_query on the stored result. Over SSH use ssh_grep." },
+      "find*": { "action": "deny", "reason": "Bash file search is disabled. Locally use the find tool (fuzzy path, or a glob in path such as 'src/**/*.ts'); to pass a file list to a program use $(git ls-files '<glob>'). Over SSH use ssh_find." },
+      "fd*": { "action": "deny", "reason": "Bash file search is disabled. Locally use the find tool (fuzzy path, or a glob in path such as 'src/**/*.ts'); to pass a file list to a program use $(git ls-files '<glob>'). Over SSH use ssh_find." },
       "git *": "ask",
       "git status*": "allow",
       "git diff*": "allow",
@@ -114,7 +113,7 @@
       "git show*": "allow",
       "git rev-parse*": "allow",
       "git ls-files*": "allow",
-      "git grep*": "deny",
+      "git grep*": { "action": "deny", "reason": "Bash content search is disabled. Locally use the grep tool (pattern + path/exclude; regex alternation for several names); to extract/dedupe/count matches, call tools.grep in codemode and process in JS; to filter command output, use overflow_query on the stored result. Over SSH use ssh_grep." },
       "git branch": "allow",
       "git branch --show-current*": "allow",
       "git remote -v": "allow",