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.
Bundles in-progress utility commands (TIME, LORA, ID, NEIGHBORS), neighbor
tracking, received_at_timestamp / personalized acks, and per-hop response
delay coordination. Tunes the coordinator so multi-hop senders actually get
responses: hop step 5s→1.5s, hop bias capped at 8s, pending TTL 15s→45s.
Verified on Heltec V3 bench bot: responds to #bot at 2, 4, and 6 hops.
BOT_PREFS_VERSION bumped 2→3, so existing bots will reset bot prefs (channel
names, known bots) to defaults on first boot of this firmware.
