[codex] Handle git pagination flags by position (#21381)

## Why

This is a follow-up to the Windows Git safe-command bypass fix for
BUGB-15601. Git's global `--paginate` / `-p` flags can route output
through a configured pager, so they should not be auto-approved as safe
before the subcommand. At the same time, `-p` after read-only
subcommands like `log`, `diff`, and `show` is the common patch-output
flag, so treating every `-p` as unsafe would make ordinary read-only
inspection commands prompt unnecessarily.

## What Changed

- Split Git option safety matching into explicit global-option and
subcommand-option lists.
- Treat global `git --paginate ...` and `git -p ...` as unsafe.
- Keep post-subcommand patch usage such as `git log -p`, `git diff -p`,
and `git show -p HEAD` safe.
- Keep the pagination coverage with the shared Git safe-command
implementation rather than the Windows wrapper tests.
- Remove the stale `git_global_option_requires_prompt` helper now that
safe-command Git option matching owns the prompt-required lists.

## Testing

- `cargo test -p codex-shell-command`

codex-rs/shell-command/src/command_safety/is_dangerous_command.rs

@@ -68,32 +68,6 @@ fn is_git_global_option_with_inline_value(arg: &str) -> bool {
     ) || ((arg.starts_with("-C") || arg.starts_with("-c")) && arg.len() > 2)
 }
 
-/// Git global options that can redirect config, repository, or helper lookup
-/// and therefore must never be auto-approved as "safe".
-pub(crate) fn git_global_option_requires_prompt(arg: &str) -> bool {
-    matches!(
-        arg,
-        // `-C` can redirect Git into a repo whose config runs helpers such as
-        // `core.fsmonitor` during read-only commands like `status`.
-        "-C" | "-c"
-            | "--config-env"
-            | "--exec-path"
-            | "--git-dir"
-            | "--namespace"
-            | "--super-prefix"
-            | "--work-tree"
-    ) || matches!(
-        arg,
-        s if ((s.starts_with("-C") || s.starts_with("-c")) && s.len() > 2)
-            || s.starts_with("--config-env=")
-            || s.starts_with("--exec-path=")
-            || s.starts_with("--git-dir=")
-            || s.starts_with("--namespace=")
-            || s.starts_with("--super-prefix=")
-            || s.starts_with("--work-tree=")
-    )
-}
-
 pub(crate) fn executable_name_lookup_key(raw: &str) -> Option<String> {
     #[cfg(windows)]
     {
@@ -200,12 +174,6 @@ mod tests {
         assert!(command_might_be_dangerous(&vec_str(&["rm", "-f", "/"])));
     }
 
-    #[test]
-    fn git_dash_c_requires_prompt() {
-        assert!(git_global_option_requires_prompt("-C"));
-        assert!(git_global_option_requires_prompt("-C/path/to/repo"));
-    }
-
     #[test]
     fn direct_powershell_words_reuse_windows_dangerous_detection() {
         let command = vec_str(&["Remove-Item", "test", "-Force"]);