Add /model list/add/remove/clear so a single provider profile can expose multiple switchable models in the TUI selector. Also add regression coverage for invalid grep regexes in the Python fallback.\n\nFixes #222\nRefs #218
glob/grep 工具的 rg 子进程 stderr 由 PIPE 改为 DEVNULL, 防止 stderr buffer 写满时子进程阻塞造成管道死锁; bash_tool 的 _read_remaining_output 加 2s 超时, 避免进程退出后读取残余输出时无限挂起 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>