MISTS: route SendAuctionMenu through WorldSession::SendAuctionHello

[MadMaxMangos]

Problem

8eaa22b ("MISTS: use SMSG_AUCTION_HELLO in SendAuctionMenu") changed the Mists arm of SendAuctionMenu to emit SMSG_AUCTION_HELLO, but kept building the packet body inline.

5.4.8 did not only split the bidirectional MSG_AUCTION_HELLO into CMSG_/SMSG_ halves — it also moved the body to the 18414 grammar. So the opcode alone is not sufficient: the inline body

data << unit->GET_GUID();      // dense GUID
data << uint32(ahEntry->ID);
data << uint8(1);

is the pre-18414 layout sent under the new opcode, and is malformed to a real 5.4.8 client. Any Lua script calling SendAuctionMenu would hit this.

Fix

MangosFour already owns a converted sender, WorldSession::SendAuctionHello, which writes the proved 18414 layout via MopAuctionPackets::BuildHello. This restores the Mists arm to call it.

This is a restoration, not a new approach — the same routing existed at fd0b208a3, which MangosFour's submodule pointer referenced before it advanced to master. fd0b208a3 is not in 8eaa22b's ancestry, so the fix was lost rather than superseded.

Non-Mists arms are unchanged, including the Cataclysm guard added in 1063f43.

Verification

MangosFour asserts this routing in mop_auction_packets_source, which fails on current master and passes with this change. Full MangosFour suite: 1076/1076.

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This change is