SSH: fix _ComaStrField length calculation

[ali-keys]

AI-Assisted: yes (Claude Sonnet 4.6)

Hi everyone,

This PR fixes SSH _ComaStrField length calculation.

_ComaStrField is used in NameList which is used with SSHKexInit:

Reproduce:

from scapy.layers.ssh import SSHKexInit, NameList

kex = SSHKexInit(kex_algorithms=NameList(names=[b"curve25519-sha256"]))
SSHKexInit(bytes(kex))  # <- error

>>> bytes(NameList(names=[b"curve25519-sha256"]))
b'\x00\x00\x00\x01curve25519-sha256'
                 ^
                 |
         incorrect length

The current implementation considers names as list and not bytes and return 1 for length in this example.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.03%. Comparing base (ab3b1bb) to head (98b0232).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5010   +/-   ##
=======================================
  Coverage   80.02%   80.03%           
=======================================
  Files         384      384           
  Lines       95622    95624    +2     
=======================================
+ Hits        76526    76532    +6     
+ Misses      19096    19092    -4     

Files with missing lines	Coverage Δ
scapy/layers/ssh.py	89.74% <100.00%> (+0.78%)	⬆️

... and 6 files with indirect coverage changes

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[polybassa]

Thanks for the PR