Fix IsDown off-by-one bug; extend the smoke test to full plugin coverage

Fix IsDown off-by-one bug; extend the smoke test to full plugin coverage

IsDown.parse_body() read words[0] (the command word "isdown" itself) as
the target URL instead of words[1] (the actual argument) - every other
plugin in the codebase treats words[0] as the command name and words[1:]
as arguments. This meant "bot: isdown <site>" always silently checked a
nonsense hostname and never replied, caught live via the extended smoke
test. Fixed, with regression test coverage mocking requests.get.

Extends tests/muc_smoke_check.py from the "complex edges" subset to
~40 checks covering nearly every registered plugin: all the deterministic
no-network ones (Pray, BOFH, Klammer, Terminate, Unicode, Slap, 8ball,
XChoose, Coin, Choose, Morse, Uptime, Info, SecurityTracker, URLBlacklist,
MentalDeficits), the network-dependent ones with generous timeouts
(Wikipedia, DuckDuckGo, Consumables/giphy, Translator, IsDown, Youtube,
URLResolver), and dedicated multi-step workflows for the stateful plugins
(Voting - ending the pre-seeded joke election and confirming a fresh vote
lands in the closing tally; VotePoll - full poll/vote/endpoll cycle with
timestamp-uniqued options and a check that skips rather than interrupts
someone else's already-active poll; Recorder - record-then-rejoin-under-
the-target-nick delivery). Deliberately excludes DidYouKnow (permanent
disk growth) and Searx (single hardcoded backend, worst-case ~17min retry
loop before failing).

Also fixes two harness bugs found while running this for real: leave_muc()
isn't a coroutine in the installed slixmpp version (was being incorrectly
awaited, crashing the Recorder workflow before it could finish), and each
stateful workflow is now individually try/excepted so one crashing doesn't
prevent the others from running and reporting.

Corrects an earlier, wrong claim (from before this was actually run live):
Recorder's delivery-on-join was assumed broken because its "userjoin.*"
binding-key entry can never match a real dotted-domain routing key - true,
but irrelevant, since Recorder also subscribes via Worker.CATCH_ALL and
receives the message regardless. Confirmed working end to end.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>