feat(devops): add Shell for SSH and console access

Connects to dev VM via SSH (default) or serial console (--console).
Supports SSH agent forwarding for credential access.

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

pkg/devops/shell.go

@@ -0,0 +1,74 @@
+package devops
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+// ShellOptions configures the shell connection.
+type ShellOptions struct {
+	Console bool     // Use serial console instead of SSH
+	Command []string // Command to run (empty = interactive shell)
+}
+
+// Shell connects to the dev environment.
+func (d *DevOps) Shell(ctx context.Context, opts ShellOptions) error {
+	running, err := d.IsRunning(ctx)
+	if err != nil {
+		return err
+	}
+	if !running {
+		return fmt.Errorf("dev environment not running (run 'core dev boot' first)")
+	}
+
+	if opts.Console {
+		return d.serialConsole(ctx)
+	}
+
+	return d.sshShell(ctx, opts.Command)
+}
+
+// sshShell connects via SSH.
+func (d *DevOps) sshShell(ctx context.Context, command []string) error {
+	args := []string{
+		"-o", "StrictHostKeyChecking=no",
+		"-o", "UserKnownHostsFile=/dev/null",
+		"-o", "LogLevel=ERROR",
+		"-A", // Agent forwarding
+		"-p", "2222",
+		"root@localhost",
+	}
+
+	if len(command) > 0 {
+		args = append(args, command...)
+	}
+
+	cmd := exec.CommandContext(ctx, "ssh", args...)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	return cmd.Run()
+}
+
+// serialConsole attaches to the QEMU serial console.
+func (d *DevOps) serialConsole(ctx context.Context) error {
+	// Find the container to get its console socket
+	c, err := d.findContainer(ctx, "core-dev")
+	if err != nil {
+		return err
+	}
+	if c == nil {
+		return fmt.Errorf("console not available: container not found")
+	}
+
+	// Use socat to connect to the console socket
+	socketPath := fmt.Sprintf("/tmp/core-%s-console.sock", c.ID)
+	cmd := exec.CommandContext(ctx, "socat", "-,raw,echo=0", "unix-connect:"+socketPath)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}