Make vim mode indicator and cursor shape configurable

Request

Please make vim-mode UI signals configurable in the Codex CLI TUI:

• Mode indicator location: expose Vim: Insert / Vim: Normal as a statusline item, e.g. vim-mode, so users can place it where they expect it, including far left.
• Cursor shape: allow choosing whether insert mode changes cursor shape or the cursor always stays block/fat.

Example:

[tui]
status_line = ["vim-mode", "model-with-reasoning", "current-dir", "git-branch"]
vim_cursor_shape = "block" # block | mode-aware

Current behavior: /statusline can reorder normal footer fields, but the vim-mode indicator and cursor behavior do not appear configurable.

Environment: Codex CLI 0.142.5, Homebrew cask, macOS / Apple Silicon.