Memo: Status Line (Read Only When Customizing a CLI Footer)

Pattern: a command spawns per update, reads session JSON on stdin (session/model/context/cwd/vim/worktree), prints the footer on stdout (multiline + ANSI allowed). Keep the command fast (<2s), debounced, non-zero-exit with empty stdout means keep previous text. Test with mock JSON piped into the script. Never load this memo for plain settings edits.