A small shell guard that blocks any command from printing the raw contents of a secret-store
file (fnox.toml or any *.env) to stdout. Agent transcripts and shell histories persist, so
even an age-encrypted fnox.toml should never be echoed.
It catches the file-read vector: cat/grep/sed/awk/head/tail/less/xxd/..., language
one-liners like open(".env"), input redirection < .env, and git diff/show/blame/log of
the file.