shell completion megaticket

[mxcl]

• [x] ~$foo<tab> (magic #608)~
• [ ] tea foo<tab> (completion for programs)
  • [x] zsh
  • [ ] bash
• [ ] tea +foo<tab> (completion for package names)
• [ ] tea foo <tab> completion for the tools themselves

[jhheider]

https://github.com/teaxyz/cli/pull/608 addresses number 1, and will make number 2 trivial. 3 should be easy, and 4 ... stupid? probably easy in zsh and hard elsewhere.