feat(protbot): add headless MHF protocol bot as cmd/protbot

Copy MHBridge into the Erupe module as cmd/protbot/ so it can be
built, tested, and maintained alongside the server. The bot
implements the full sign → entrance → channel login flow and
supports lobby entry, chat, session setup, and quest enumeration.

The conn/ package keeps its own Blowfish crypto primitives to avoid
importing erupe-ce/config (which requires a config file at init).

cmd/protbot/scenario/session.go

@@ -0,0 +1,50 @@
+package scenario
+
+import (
+	"fmt"
+	"time"
+
+	"erupe-ce/cmd/protbot/protocol"
+)
+
+// SetupSession performs the post-login session setup: ISSUE_LOGKEY, RIGHTS_RELOAD, LOADDATA.
+// Returns the loaddata response blob for inspection.
+func SetupSession(ch *protocol.ChannelConn, charID uint32) ([]byte, error) {
+	// Step 1: Issue logkey.
+	ack := ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_SYS_ISSUE_LOGKEY (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildIssueLogkeyPacket(ack)); err != nil {
+		return nil, fmt.Errorf("issue logkey send: %w", err)
+	}
+	resp, err := ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("issue logkey ack: %w", err)
+	}
+	fmt.Printf("[session] ISSUE_LOGKEY ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	// Step 2: Rights reload.
+	ack = ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_SYS_RIGHTS_RELOAD (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildRightsReloadPacket(ack)); err != nil {
+		return nil, fmt.Errorf("rights reload send: %w", err)
+	}
+	resp, err = ch.WaitForAck(ack, 10*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("rights reload ack: %w", err)
+	}
+	fmt.Printf("[session] RIGHTS_RELOAD ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	// Step 3: Load save data.
+	ack = ch.NextAckHandle()
+	fmt.Printf("[session] Sending MSG_MHF_LOADDATA (ackHandle=%d)...\n", ack)
+	if err := ch.SendPacket(protocol.BuildLoaddataPacket(ack)); err != nil {
+		return nil, fmt.Errorf("loaddata send: %w", err)
+	}
+	resp, err = ch.WaitForAck(ack, 30*time.Second)
+	if err != nil {
+		return nil, fmt.Errorf("loaddata ack: %w", err)
+	}
+	fmt.Printf("[session] LOADDATA ACK (error=%d, %d bytes)\n", resp.ErrorCode, len(resp.Data))
+
+	return resp.Data, nil
+}