quak backup retries failed requests for longer (closes #165)

src/retry.ts exports UNATTENDED_RETRY_OPTIONS beside the unchanged
default: 10 attempts, a 1 s base delay and a 60 s cap, so a request that
keeps failing waits at most 243 s before it gives up. bin/quak.ts loads
the backup's session with them, so its refresh, ML data and downloads
all use them; every other command keeps the default. What is retried
and the backoff formula are unchanged.

Model: opus-5-5

README.md

@@ -420,18 +420,24 @@ Backoff is exponential with full jitter: the delay before retry _n_ is
 `random() * min(maxDelayMs, baseDelayMs * 2 ** (n - 1))`. The exponential term
 is the ceiling and the wait is drawn below it, so a client that lost many
 parallel downloads to one CDN blip does not send them all again at the same
-instant. Defaults, configurable through `ApiClientOptions.retry`:
+instant. The numbers, configurable through `ApiClientOptions.retry`:
 
-| Option        | Default | Meaning                             |
-| ------------- | ------- | ----------------------------------- |
-| `attempts`    | `4`     | total calls, not retries            |
-| `baseDelayMs` | `500`   | ceiling for the first retry's delay |
-| `maxDelayMs`  | `10000` | upper bound on that ceiling         |
+| Option        | Default | `quak backup` | Meaning                             |
+| ------------- | ------- | ------------- | ----------------------------------- |
+| `attempts`    | `4`     | `10`          | total calls, not retries            |
+| `baseDelayMs` | `500`   | `1000`        | ceiling for the first retry's delay |
+| `maxDelayMs`  | `10000` | `60000`       | upper bound on that ceiling         |
 
-With those defaults a file that is going to fail gives up after at most three
-and a half seconds of waiting. `sleep` and `random` are injectable through the
-same option, which is how the test suite exercises the whole policy without
-waiting.
+With the defaults a file that is going to fail gives up after at most three and
+a half seconds of waiting. `quak backup` usually runs from cron with nobody
+watching, so every request it makes uses the `quak backup` column instead,
+exported as `UNATTENDED_RETRY_OPTIONS`: a request that keeps failing gives up
+after at most 243 seconds of waiting, and usually after about half that, since
+each wait is drawn at random below its ceiling. Every other command uses the
+defaults. A library user gets the same budget by passing
+`UNATTENDED_RETRY_OPTIONS` as `ApiClientOptions.retry`. `sleep` and `random` are
+injectable through the same option, which is how the test suite exercises the
+whole policy without waiting.
 
 Two deadlines, renewed for each attempt: