pub fn discover_codex_binary(configured: Option<&str>) -> Result<PathBuf>Expand description
Locate a working codex binary.
Order: configured → KRANZ_CODEX_BIN env var → codex on PATH →
well-known install locations. Each candidate is validated by running it
with --version; the first one that succeeds wins. Errors list every
attempt so the user can see what was tried.
KRANZ_CODEX_BIN, when set and non-empty, is an exclusive override: only
that path is probed, and a failure is returned immediately rather than
falling through to PATH or the well-known fallback locations. Naming the
binary explicitly and having it not work is an error, not a reason to
search elsewhere.