refactor(cli): add Fatal() and simplify main entry point

- Add cli.Fatal(err) that prints styled error and exits
- Change cli.Main() to handle errors internally via Fatal()
- Simplify main.go to just: cli.Main()

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

main.go

@@ -1,9 +1,6 @@
 package main
 
 import (
-	"fmt"
-	"os"
-
 	"github.com/host-uk/core/pkg/cli"
 
 	// Build variants import commands via self-registration.
@@ -12,8 +9,5 @@ import (
 )
 
 func main() {
-	if err := cli.Main(); err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
+	cli.Main()
 }

pkg/cli/app.go

@@ -17,7 +17,8 @@ const (
 
 // Main initialises and runs the CLI application.
 // This is the main entry point for the CLI.
-func Main() error {
+// Exits with code 1 on error.
+func Main() {
 	// Initialise CLI runtime with services
 	if err := Init(Options{
 		AppName: AppName,
@@ -29,14 +30,14 @@ func Main() error {
 			})),
 		},
 	}); err != nil {
-		return err
+		Fatal(err)
 	}
 	defer Shutdown()
 
 	// Add completion command to the CLI's root
 	RootCmd().AddCommand(completionCmd)
 
-	return Execute()
+	Fatal(Execute())
 }
 
 // completionCmd generates shell completion scripts.

pkg/cli/runtime.go

@@ -156,6 +156,14 @@ func Error(msg string) {
 	fmt.Println(ErrorStyle.Render(SymbolCross + " " + msg))
 }
 
+// Fatal prints an error message and exits with code 1.
+func Fatal(err error) {
+	if err != nil {
+		Error(err.Error())
+		os.Exit(1)
+	}
+}
+
 // Warning prints a warning message.
 func Warning(msg string) {
 	fmt.Println(WarningStyle.Render(SymbolWarning + " " + msg))