Shell completion support

Shell completions turn mytool dep<TAB> into mytool deploy and mytool deploy --en<TAB> into mytool deploy --environment. Power users depend on them; new users discover commands through them. A CLI with twelve subcommands and no completion support forces users to consult --help for every invocation. Completion scripts are cheap to generate (one line in cobra, one crate in clap, built into oclif) and disproportionately improve daily use.

Add a completions subcommand that emits bash/zsh/fish scripts to stdout, and document the install one-liner in README. For cobra in cmd/completion.go:

var completionCmd = &cobra.Command{
    Use: "completion [bash|zsh|fish]",
    RunE: func(cmd *cobra.Command, args []string) error {
        return rootCmd.GenBashCompletion(os.Stdout)
    },
}

Users install with mytool completion bash > /etc/bash_completion.d/mytool.

• ID: shell-completions

• Severity: info

• What to look for: List all completion script generation capabilities. check for shell completion generation or documentation. In commander, check for program.enablePositionalOptions() or completion plugins. In oclif, completions are built-in. In cobra, check for GenBashCompletion / GenZshCompletion / GenFishCompletion methods. In clap, check for generate function from clap_complete. Look for a completions or completion subcommand, or documentation about shell completion setup.

• Pass criteria: The CLI provides shell completion scripts via a subcommand (mytool completions bash), a --completions flag, or has completion setup documented. At least bash and zsh are supported — at least 1 shell completion script (bash, zsh, or fish) should be generated or provided. Report: "X shell completion scripts available."

• Fail criteria: No shell completion support and no documentation about completion setup.

• Skip (N/A) when: The CLI has 2 or fewer commands with no complex options — completion adds little value. All checks skip when no CLI entry point is detected.

• Detail on fail: "No shell completion support found — no 'completions' subcommand, no completion generation, and no documentation for completion setup"

• Remediation: Shell completions dramatically improve the user experience for CLIs with many commands:

  // Node.js — tabtab or omelette for completions
  // Or with oclif, completions are built in:
  // mytool autocomplete bash
  
  // cobra (Go) — built-in completion generation
  var completionCmd = &cobra.Command{
      Use:   "completion [bash|zsh|fish|powershell]",
      Short: "Generate shell completion scripts",
      RunE: func(cmd *cobra.Command, args []string) error {
          switch args[0] {
          case "bash":
              return rootCmd.GenBashCompletion(os.Stdout)
          case "zsh":
              return rootCmd.GenZshCompletion(os.Stdout)
          }
          return nil
      },
  }
  

  // clap (Rust) — clap_complete crate
  use clap_complete::{generate, shells::Bash};
  generate(Bash, &mut cli, "mytool", &mut io::stdout());