Node's `fetch` rejects every failure below HTTP as `fetch failed` and puts
the reason on `cause`. `describeError` in `src/errors.ts` gives the message
followed by the messages on the cause chain, and for an `AggregateError`,
which Node gives when every address of a host fails, the message of each
address. `run` prints it, and the backup logs and records it. `classify`
reads that text and calls a failure transient when `hasTransportCode`, now
exported by `src/retry.ts`, finds a transport errno on the chain. A failed
ML data fetch keeps its error as the cause. The bounded walk along the
chain moved from `src/retry.ts` to `src/errors.ts`.
A truncated download's message leaves the authentication failure to its
cause.
Model: opus-5-5
A 401 from the server that ends a command reaches run in src/cli-run.ts as
an ApiError; run prints one line saying to run "quak login" and exits 3.
quak backup meets it on its first refresh, before it touches any file. For
the commands that load the saved session, a missing or corrupt session file
keeps its message and also exits 3.
Judgement call: quak logout is unchanged; it handles its own errors and
deletes the session file whatever the server answers.
Judgement call: quak backup still prints its two progress lines before the
error line.
Model: opus-5-5
An error a command throws now reaches the user as one `quak: MESSAGE`
line on stderr, and the CLI exits 1 once output has drained. The wrapper
moved from bin/quak.ts to src/cli-run.ts so it can be tested, and
bin/quak.ts awaits program.parseAsync() so async actions are awaited.
Model: opus-5-5