feat: add shell-completions subcommand

[lamchau]

extracted from an experimental 'daemon/lsp mode' branch which may overhaul how session management is handled. at the very least, landing this would be a good starting point to enable discoverability of commands and adoption.

• shell-completions --install support for bash, fish, or zsh (appends to standard config files)
• shell-completions --generate support for bash, fish, or zsh (custom location with install text)
• support for goose session resume <session_name>

this can only be tested via an entrypoint (i.e. installed not via uv)

pipx install . --preinstall goose-plugins-block --force

Usage

This will install to the set user-defined $SHELL

goose shell-completions --install

Usage: goose shell-completions [OPTIONS] [[bash|zsh|fish]]

  Manage shell completions for goose

Options:
  --install   Install shell completions
  --generate  Generate shell completions
  --help      Show this message and exit.

Note: For bash and zsh, the user will need to source {rc_file} before it can take effect.

Alternatively, you can generate the completions and manually install run them yourself

goose shell-completions --generate bash > path/to/custom-bash
goose shell-completions --generate fish > path/to/completion.fish
goose shell-completions --generate zsh > path/to/custom-zsh

Example installations with autocompletion per $SHELL

Guard for exclusive options --generate or --install only

Autocomplete for session (via fish; goose session resume a<tab>)

[baxen]

LGTM