v3.22.4: the proactive-drain pending exemption

The runner's unexpected-pending-command guard fired for any non-expect step,
so a proactive-drain after a step that answered 91XX failed with
"unexpected proactive command pending (SW 91XX) - add an expect step or a
status action" - contradicting the drain's own doc ("consume whatever the
card announces") and the v3.22.2 RAM recipe ("an expect or a proactive-drain").

The guard now exempts a proactive-drain step: its STATUS poll re-announces
the unfetched command, fetches and answers it, and the drain's final-SW and
pending handling is unchanged (a still-pending card is handed to the next
step, an idle card passes).  No pending-length plumbing: STATUS-first keeps
the drain's attempts/log semantics and tolerates a card that dropped the
command.  The guard note now names the drain instead of the misleading
"status action" (a status action in that position also trips the guard).

Docs: the drain section in test-scripts.md, api.md's action list and the
help EN/RU drain bullet.  Tests: 839 frontend + 819 Python; sw cache
simple-v408.

docs/api.md

@@ -743,7 +743,9 @@ mask `91??`, i.e. poll until the card announces a command) or `proactive-drain`
 optional `require` `{command, qualifier?}` asserting at least one drained
 command; the final SW is the step's `check.sw`, so a still-pending card fails
 and hands the command to the next step - an empty drain passes unless
-`require` was given).
+`require` was given).  It is exempt from the runner's
+unexpected-pending-command guard, so it also consumes a command a previous
+step left pending (`91XX`).
 
 `check` is `{"sw": ..., "data": ...}` (exact or `{"mode": "mask", "value":
 "91??"}`, `?` = per-nibble wildcard) plus `"por"` for SCP80 -