The provider-settings descriptor gate rejected `kind: "secret"` in the
generic field writer, but it still accepted a text, number, enum, or
boolean field whose writeCommand was `codexbar config set-api-key ...
{value}`. A mislabeled descriptor would then put the typed API key in
the command line, which /proc/<pid>/cmdline exposes while it runs.

Only a secret field, which writes through the stdin prompt, may now use
set-api-key: normalization drops any other kind with that subcommand,
and the write plan refuses one mutated after normalization with
`unsupportedCommand`.

Documentation: the descriptor contract's Plasma rules state the
restriction. No CHANGELOG entry: no released CLI emits descriptors yet
(0.65.0 still rejects `config providers --descriptors`), so nothing
observable changes today.


Claude-Session: https://claude.ai/code/session_01TvjnVJPgkwU6fxn8uL6N8c

Co-authored-by: Claude <noreply@anthropic.com>