refactor codebase and fix bugs

- merge dante.go and dante_control.go into single dante.go
- consolidate buildDantePacket and buildDantePacket28 into one function
- fix broken comparison logic in SetDanteClockMaster
- split ARP parsing into platform-specific files with build tags
- implement Linux ARP table parsing via /proc/net/arp
- run gofmt on all files

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

arp.go

@@ -1,12 +1,9 @@
 package tendrils
 
 import (
-	"bufio"
 	"context"
 	"log"
 	"net"
-	"os/exec"
-	"runtime"
 	"strings"
 	"time"
 )
@@ -54,69 +51,6 @@ func (t *Tendrils) readARPTable() {
 	}
 }
 
-func (t *Tendrils) parseARPTable() []arpEntry {
-	if runtime.GOOS == "darwin" {
-		return t.parseARPDarwin()
-	}
-	return t.parseARPLinux()
-}
-
-func (t *Tendrils) parseARPDarwin() []arpEntry {
-	cmd := exec.Command("arp", "-an")
-	output, err := cmd.Output()
-	if err != nil {
-		return nil
-	}
-
-	var entries []arpEntry
-	scanner := bufio.NewScanner(strings.NewReader(string(output)))
-	for scanner.Scan() {
-		line := scanner.Text()
-
-		if strings.Contains(line, "permanent") {
-			continue
-		}
-
-		fields := strings.Fields(line)
-		if len(fields) < 6 {
-			continue
-		}
-
-		ipStr := strings.Trim(fields[1], "()")
-		ip := net.ParseIP(ipStr)
-		if ip == nil {
-			continue
-		}
-
-		macStr := fields[3]
-		if macStr == "(incomplete)" {
-			continue
-		}
-
-		macStr = normalizeMACAddress(macStr)
-		mac, err := net.ParseMAC(macStr)
-		if err != nil {
-			log.Printf("[arp] failed to parse MAC %q for IP %s: %v", macStr, ipStr, err)
-			continue
-		}
-
-		ifaceName := fields[5]
-
-		entries = append(entries, arpEntry{
-			ip:    ip,
-			mac:   mac,
-			iface: ifaceName,
-		})
-	}
-
-	return entries
-}
-
-func (t *Tendrils) parseARPLinux() []arpEntry {
-	var entries []arpEntry
-	return entries
-}
-
 func normalizeMACAddress(mac string) string {
 	parts := strings.Split(mac, ":")
 	for i, part := range parts {