You cannot see the DAgent until you login because your unattend.xml isn't installing the DAgent until you login.
And you said you used the scripted_install=1 parameter but I can't see it in your command line, but if you aren't installing the DAgent until you log in it's probably not necessary.
The built in Scripted install job uses setupcomplete in:
\Deployment Server\Deploy\WinOS005\sources\sources\$OEM$\$$\Setup\Scripts
to install the DAgent. This way it's installed after all the other Setup commands and config have run and DS can then do post deployment config without conflicting with Windows Setup.
I've amended the default command to turn on DAgent logging:
C:\DAgent\DAgent.msi /quiet server_tcp_addr=DSAlias server_tcp_port=402 scripted_install=1 LAUNCHUI=FALSE LOGERRORS=1 LOGFILE="C:\Program Files\Altiris\Dagent\DAgent.log" LOGINFORMATION=1 LOGSIZE=512
The DAgent msi is in:
\Deployment Server\Deploy\WinOS005\sources\sources\$OEM$\$1\DAgent