os-tayga: IPv6 Interface Address field breaks when CIDR suffix entered (double /128 appended)

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Describe the bug
IPv6 Interface Address field breaks when CIDR suffix entered (double /128 appended)

To Reproduce
enter an address like fd00:6464::1/126 in the "IPv6 NAT64 Interface Address" field, save, restart the service

Expected behavior
interface should get the IPv6 address applied correctly

Screenshots
ifconfig: fd00:6464::1/126: bad value error, resulting IFDISABLED interface state

Relevant log files
root@opnsense:~ # ifconfig nat64
nat64: flags=1008051<UP,POINTOPOINT,RUNNING,MULTICAST,LOWER_UP> metric 0 mtu 1500
options=4080000<LINKSTATE,MEXTPG>
inet 192.168.254.2 --> 192.168.254.1 netmask 0xffffffff
groups: tun tayga
nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
Opened by PID 62232

Environment
Software version used
OPNsense 26.7.1 (amd64).
os-tayga: rev 1.5

Start at the os-tayga configuration entry point for the “IPv6 NAT64 Interface Address” field and trace how an entered CIDR address is saved and passed to the service. Reproduce with fd00:6464::1/126, then verify that restarting the service applies the address without appending an extra /128 and avoids the IFDISABLED state.