cli QoL: vm prune, list→ls aliases, delete→rm aliases

- `banger vm prune` sweeps every non-running VM (stopped, created,
  error) with an interactive confirmation; -f/--force skips the prompt.
  Partial failures report which VM failed and exit non-zero.
- list commands gain `ls` alias: vm list already had it; added to image
  list, kernel list, and vm session list.
- delete commands gain `rm` alias: vm delete and image delete. kernel
  rm already aliased delete/remove.

Uses new test seams (vmListFunc) plus the existing vmDeleteFunc so
prune unit-tests without touching the daemon socket.

internal/cli/aliases_test.go

@@ -0,0 +1,103 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+// findSubcommand walks cmd's subtree along path and returns the
+// matching command, or nil.
+func findSubcommand(root *cobra.Command, path ...string) *cobra.Command {
+	cur := root
+	for _, name := range path {
+		var next *cobra.Command
+		for _, sub := range cur.Commands() {
+			if sub.Name() == name {
+				next = sub
+				break
+			}
+		}
+		if next == nil {
+			return nil
+		}
+		cur = next
+	}
+	return cur
+}
+
+func assertHasAlias(t *testing.T, cmd *cobra.Command, alias string) {
+	t.Helper()
+	if cmd == nil {
+		t.Fatal("command is nil")
+	}
+	for _, a := range cmd.Aliases {
+		if a == alias {
+			return
+		}
+	}
+	t.Errorf("%q missing alias %q; have %v", cmd.Name(), alias, cmd.Aliases)
+}
+
+func TestListCommandsHaveLsAlias(t *testing.T) {
+	root := NewBangerCommand()
+
+	cases := [][]string{
+		{"vm", "list"},
+		{"image", "list"},
+		{"kernel", "list"},
+		{"vm", "session", "list"},
+	}
+	for _, path := range cases {
+		t.Run(path[len(path)-1], func(t *testing.T) {
+			cmd := findSubcommand(root, path...)
+			if cmd == nil {
+				t.Fatalf("missing command: %v", path)
+			}
+			assertHasAlias(t, cmd, "ls")
+		})
+	}
+}
+
+func TestDeleteCommandsHaveRmAlias(t *testing.T) {
+	root := NewBangerCommand()
+
+	cases := [][]string{
+		{"vm", "delete"},
+		{"image", "delete"},
+	}
+	for _, path := range cases {
+		t.Run(path[len(path)-1], func(t *testing.T) {
+			cmd := findSubcommand(root, path...)
+			if cmd == nil {
+				t.Fatalf("missing command: %v", path)
+			}
+			assertHasAlias(t, cmd, "rm")
+		})
+	}
+}
+
+func TestVMCommandRegistersPrune(t *testing.T) {
+	root := NewBangerCommand()
+	cmd := findSubcommand(root, "vm", "prune")
+	if cmd == nil {
+		t.Fatal("vm prune not registered")
+	}
+	if flag := cmd.Flags().Lookup("force"); flag == nil {
+		t.Error("vm prune missing --force flag")
+	}
+	if flag := cmd.Flags().ShorthandLookup("f"); flag == nil {
+		t.Error("vm prune missing -f shorthand")
+	}
+}
+
+func TestKernelRmHasDeleteAlias(t *testing.T) {
+	// This already existed prior to this feature — guard against regressions.
+	root := NewBangerCommand()
+	cmd := findSubcommand(root, "kernel", "rm")
+	if cmd == nil {
+		t.Fatal("kernel rm missing")
+	}
+	assertHasAlias(t, cmd, "delete")
+	assertHasAlias(t, cmd, "remove")
+}