v0.5.0

Release the stream decoder's tolerance for lines it does not read, and let a
codex run say which profile it authenticates as.

The decoder reads a line's type on its own before decoding anything else, so a
bookkeeping event whose message is a bare string is skipped rather than
failing the run. A modelled line whose shape is unreadable is surfaced as an
event instead, and only the terminal line stays fatal. This shipped to main
before v0.4.0 was cut against the older decoder, which turned a working stream
into ErrProviderUnavailable for any consumer pinned there.

codex.WithConfigDir exports CODEX_HOME, matching the option claudecode already
had. CODEX_HOME redirects the whole Codex profile rather than settings alone,
so it carries the credential too: a profile holding a session outranks the
token Isolated injects, and HOME is left to Driver.WithHome because codex needs
no second variable to find its cache.

Full changelog: v0.4.0...v0.5.0