#560

docs(cli): shorten the main help and keep proxy options under proxy --help

Openlahfirwants to merge intofrom
  1. portless --help ran to about 226 lines and listed proxy start options such as -p and --tld that the root command rejects.
  2. The main help is now 64 lines with only the options the root command accepts, points to portless proxy --help for proxy options, and states how flags, environment variables, and portless.json take precedence.
  3. Builds on #559.