v0.3.5

feat(venv): enter/resume/shell now spawn an activated interactive shell

Replace the eval-snippet approach with a real activated subshell: cd to the
project root, source the venv activate script, set VIRTUAL_ENV / PATH / prompt.
Works for bash (--rcfile), zsh (ZDOTDIR), and fish (-C); a --print flag
keeps the old eval snippet for non-interactive use.  Shell is now an alias
of enter.  All help/info/status messages updated to remove eval references.