fix(ipv6-opts): _make_opt_smf_dpd overwrites the parsed DPD mode, so H-DPD rebuilds as I-DPD #1190

Describe the bug
_make_opt_smf_dpd drops the parsed DPD mode. It sets dpd_type = opt.dpd_type (pcapkit/protocols/internet/hopopt.py:1606) and then overwrites it at :1611 from the mode keyword, whose default is I-DPD. A parsed H-DPD option therefore rebuilds as I-DPD. ipv6_opts.py has the same code.

To Reproduce
On origin/main, build an H-DPD SMF_DPD option (mode=H_DPD, hav=01020304), parse it, and rebuild it with from_data. The original bytes are 3b00080481020304. The rebuild is 3b00080100010100: I-DPD with a null tagger ID. HOPOPT and IPv6_Opts behave the same.

Expected behavior
A parsed SMF_DPD option keeps its mode and rebuilds byte-exactly.

Found by the #1187 worker. The #1187 cross-review reproduced it. I read both lines on main.