refactor(prompts): fold Asker into Prompter and share delete confirmations

FormPrompter is the only production prompter and implements the rich
prompt API, so Ask, AskText and ConfirmDefault become the Prompter
interface and the plain Input/Confirm fallbacks go away.

Confirmations that default to no derive their non-terminal wording
from the prompt, and single deletes share deleteConfirmed for the
prompt, the request and the done line.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/ssh_keys.go

@@ -223,14 +223,7 @@ $ tea ssh-key delete 2 --yes`,
 			if err != nil {
 				return err
 			}
-			if err := a.confirmAction(cmd, terminal.Confirmation{Prompt: "Delete " + sshKeyLabel(key) + "?", NonTTY: "delete " + sshKeyLabel(key)}); err != nil {
-				return err
-			}
-			if err := service.Delete(cmd.Context(), id); err != nil {
-				return err
-			}
-			a.done(cmd, "Deleted %s", sshKeyLabel(key))
-			return nil
+			return a.deleteConfirmed(cmd, sshKeyLabel(key), func() error { return service.Delete(cmd.Context(), id) })
 		},
 	}
 }