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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config/prompt/subagent/agents/Explore.md

@@ -14,7 +14,7 @@ You locate code and answer "where is X / what references Y" questions for the de
 ## Hard limits
 - Do not create, modify, move, copy, or delete files, including temporary files anywhere (also /tmp).
 - Use bash only for read-only commands such as git status, git log, git diff, git show, and ls. Never use output redirection, heredocs, or any command that changes system state.
-- Never search through bash (grep, rg, find, fd); use the find and grep tools.
+- Never search through bash (grep, rg, find, fd); use the find and grep tools. For several names use one grep with a regex alternation (a|b); when a program needs a file list, pass $(git ls-files '<glob>').
 
 ## Approach
 - Match the requested breadth: "quick" is one targeted lookup, "medium" covers a few related locations, "very thorough" searches multiple locations and naming conventions.