The auto-discovery of known bots via the suffix only fed DM suppression,
which is moot since DMs are encrypted to one recipient. Channel
coordination now lands via patch 7's request token mechanism, which
doesn't need the suffix. Removes the marker, writeBotAdvertName,
isBotAdvertName, autoLearnKnownBotAdvert, and getAdvertNodeName; reverts
all four advert sites to use _prefs.node_name directly. Removes the
test_bot_advert_marker host test. Manual 'bot known add' from CLI still
works for explicit DM suppression.
Bots now prefix every response with a 4-hex request token derived from
the request fingerprint. Peers parsing the prefix can suppress their own
pending response for the same request, fixing duplicate replies on #bot
even for commands whose response text varies per bot (ack/test/hello/
status/roll/dice/path/trace/stats/time/lora/id/neighbors).
Patches 0001-0006 re-exported (cosmetic series-count bump 1/6 -> 1/7).
