fix(cli): show error/hide help for unsupported subcommands (#10760) (#12624)

Fixes #10760 

The coder CLI quietly accepts any subcommand arguments and silently swallows them.

Currently:
```sh
❯ coder | head -n5
coder v2.3.3+e491217

USAGE:
  coder [global-flags] <subcommand>
```

```sh
❯ coder idontexist | head -n5
coder v2.3.3+e491217

USAGE:
  coder [global-flags] <subcommand>
```

Now help output will not be show when there is an unknown subcommand error. Instead users will be given the command for the help output.

```sh
❯ coder idontexist
Encountered an error running "coder", see "coder --help" for more information 
error: unrecognized subcommand "idontexist"
```
```sh
❯ coder iexistbut idontexist
Encountered an error running "coder iexistbut", see "coder iexistbut --help" for more information 
error: unrecognized subcommand "idontexist"
```

Also this stuff: `Encountered an error running "coder iexistbut"... ` gets written to `os.Stdout` in `prettyErrorFormatter{w: os.Stderr, verbose: r.verbose}`, not sure how to test that output.

cli/help.go

@@ -4,7 +4,9 @@ import (
 	"bufio"
 	_ "embed"
 	"fmt"
+	"os"
 	"regexp"
+	"slices"
 	"sort"
 	"strings"
 	"text/tabwriter"
@@ -320,6 +322,25 @@ var usageWantsArgRe = regexp.MustCompile(`<.*>`)
 // output for a given command.
 func helpFn() serpent.HandlerFunc {
 	return func(inv *serpent.Invocation) error {
+		// Check for invalid subcommands before printing help.
+		if len(inv.Args) > 0 && !usageWantsArgRe.MatchString(inv.Command.Use) {
+			_, _ = fmt.Fprintf(inv.Stderr, "---\nerror: unrecognized subcommand %q\n", inv.Args[0])
+		}
+		if len(inv.Args) > 0 {
+			// Return an error so that exit status is non-zero when
+			// a subcommand is not found.
+			err := xerrors.Errorf("unrecognized subcommand %q", strings.Join(inv.Args, " "))
+			if slices.Contains(os.Args, "--help") {
+				// Subcommand error is not wrapped in RunCommandErr if command
+				// is invoked with --help with no HelpHandler
+				return &serpent.RunCommandError{
+					Cmd: inv.Command,
+					Err: err,
+				}
+			}
+			return err
+		}
+
 		// We use stdout for help and not stderr since there's no straightforward
 		// way to distinguish between a user error and a help request.
 		//
@@ -340,9 +361,6 @@ func helpFn() serpent.HandlerFunc {
 		if err != nil {
 			return err
 		}
-		if len(inv.Args) > 0 && !usageWantsArgRe.MatchString(inv.Command.Use) {
-			_, _ = fmt.Fprintf(inv.Stderr, "---\nerror: unknown subcommand %q\n", inv.Args[0])
-		}
 		return nil
 	}
 }