feat: add shell completion scripts for Zsh, Bash, and Fish

CHANGES:
- Add shell completion support for three major shells
- Create standardized completion scripts in completions/ directory
- Add --shell-complete-list flag for machine-readable output
- Update Print() methods to support plain output format
- Document installation steps for each shell in README
- Replace old fish completion script with improved version

plugins/tools/defaults.go

@@ -47,7 +47,7 @@ func (o *Defaults) Setup() (err error) {
 		return
 	}
 
-	vendorsModels.Print()
+	vendorsModels.Print(false)
 
 	if err = o.Ask(o.Name); err != nil {
 		return