Remove opencode package + vm acp command (dead code)

The `internal/opencode` package and the `opencodeCapability` that
consumed it were hard-wired to wait for opencode on guest port 4096
when an image shipped an initrd. After the prune commits (void /
alpine / customize.sh / image build all removed), nothing banger
produces today carries an initrd, so the capability's wait path was
unreachable: every startup short-circuited to the "direct-boot, skip
opencode" branch.

Same logic for `banger vm acp`: it SSHes to `opencode acp --cwd
<path>`, a binary the golden image no longer ships. Users who run
their own image with opencode can still invoke
`ssh vm -- opencode acp --cwd /root/repo` directly — no banger
scaffolding required.

Removed:
- internal/opencode/ (whole package, 255 LOC incl. tests)
- internal/daemon/opencode.go (opencodeCapability)
- cli `vm acp` command + its helpers (runVMACP, sshACPCommandArgs,
  vmACPRemoteCommand) + their tests
- The opencodeCapability{} entry in registeredCapabilities() plus
  the test that pinned its presence
- `wait_opencode` progress-stage label from the vm-create renderer
- Stale mentions in daemon/doc.go, README, and webui test fixtures

~480 lines gone, 12 added. `banger/internal` is now 25 packages
instead of 26.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/cli/banger.go

@@ -736,7 +736,6 @@ func newVMCommand() *cobra.Command {
 		newVMActionCommand("delete", "Delete a VM", "vm.delete"),
 		newVMSetCommand(),
 		newVMSSHCommand(),
-		newVMACPCommand(),
 		newVMWorkspaceCommand(),
 		newVMSessionCommand(),
 		newVMLogsCommand(),
@@ -1140,27 +1139,6 @@ func newVMSSHCommand() *cobra.Command {
 	}
 }
 
-func newVMACPCommand() *cobra.Command {
-	var cwd string
-	cmd := &cobra.Command{
-		Use:   "acp <id-or-name>",
-		Short: "Bridge local stdio to guest opencode acp over SSH",
-		Args:  exactArgsUsage(1, "usage: banger vm acp [--cwd PATH] <id-or-name>"),
-		RunE: func(cmd *cobra.Command, args []string) error {
-			layout, cfg, err := ensureDaemon(cmd.Context())
-			if err != nil {
-				return err
-			}
-			if err := validateSSHPrereqs(cfg); err != nil {
-				return err
-			}
-			return runVMACP(cmd.Context(), layout.SocketPath, cfg, cmd.InOrStdin(), cmd.OutOrStdout(), cmd.ErrOrStderr(), args[0], cwd)
-		},
-	}
-	cmd.Flags().StringVar(&cwd, "cwd", "", "guest working directory for opencode acp")
-	return cmd
-}
-
 func newVMWorkspaceCommand() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "workspace",
@@ -2497,18 +2475,6 @@ func runSSHSession(ctx context.Context, socketPath, vmRef string, stdin io.Reade
 	return sshErr
 }
 
-func runVMACP(ctx context.Context, socketPath string, cfg model.DaemonConfig, stdin io.Reader, stdout, stderr io.Writer, idOrName, cwd string) error {
-	result, err := vmSSHFunc(ctx, socketPath, idOrName)
-	if err != nil {
-		return err
-	}
-	sshArgs, err := sshACPCommandArgs(cfg, result.GuestIP, vmACPRemoteCommand(cwd))
-	if err != nil {
-		return err
-	}
-	return sshExecFunc(ctx, stdin, stdout, stderr, sshArgs)
-}
-
 func shouldCheckSSHReminder(err error) bool {
 	if err == nil {
 		return true
@@ -2544,30 +2510,6 @@ func sshCommandArgs(cfg model.DaemonConfig, guestIP string, extra []string) ([]s
 	return args, nil
 }
 
-func sshACPCommandArgs(cfg model.DaemonConfig, guestIP, remoteCommand string) ([]string, error) {
-	if guestIP == "" {
-		return nil, errors.New("vm has no guest IP")
-	}
-	args := []string{"-T", "-F", "/dev/null"}
-	if cfg.SSHKeyPath != "" {
-		args = append(args, "-i", cfg.SSHKeyPath)
-	}
-	args = append(
-		args,
-		"-o", "IdentitiesOnly=yes",
-		"-o", "BatchMode=yes",
-		"-o", "PreferredAuthentications=publickey",
-		"-o", "PasswordAuthentication=no",
-		"-o", "KbdInteractiveAuthentication=no",
-		"-o", "StrictHostKeyChecking=no",
-		"-o", "UserKnownHostsFile=/dev/null",
-		"-o", "LogLevel=ERROR",
-		"root@"+guestIP,
-		"bash", "-lc", remoteCommand,
-	)
-	return args, nil
-}
-
 func validateSSHPrereqs(cfg model.DaemonConfig) error {
 	checks := system.NewPreflight()
 	checks.RequireCommand("ssh", "install openssh-client")
@@ -3175,24 +3117,6 @@ func printVMRunWarning(out io.Writer, detail string) {
 	_, _ = fmt.Fprintln(out, "[vm run] warning: "+detail)
 }
 
-func vmACPRemoteCommand(cwd string) string {
-	var script strings.Builder
-	script.WriteString("set -euo pipefail\n")
-	if strings.TrimSpace(cwd) != "" {
-		fmt.Fprintf(&script, "DIR=%s\n", shellQuote(cwd))
-	} else {
-		fmt.Fprintf(&script, "REPO_DIR=%s\n", shellQuote(vmRunGuestDir()))
-		fmt.Fprintf(&script, "DEFAULT_DIR=%s\n", shellQuote("/root"))
-		script.WriteString(`if [ -d "$REPO_DIR" ]; then DIR="$REPO_DIR"; else DIR="$DEFAULT_DIR"; fi
-`)
-	}
-	script.WriteString(`cd "$DIR"
-`)
-	script.WriteString(`exec opencode acp --cwd "$DIR"
-`)
-	return script.String()
-}
-
 func shellQuote(value string) string {
 	return "'" + strings.ReplaceAll(value, "'", `'"'"'`) + "'"
 }
@@ -3530,8 +3454,6 @@ func vmCreateStageLabel(stage string) string {
 		return "waiting for vsock agent"
 	case "wait_guest_ready":
 		return "waiting for guest services"
-	case "wait_opencode":
-		return "waiting for opencode"
 	case "apply_dns":
 		return "publishing dns"
 	case "apply_nat":