feat: add gt up/down commands and daemon doctor check

New commands:
- `gt up` - Idempotent boot command that brings up all services:
  Daemon, Deacon, Mayor, and Witnesses for all rigs
- `gt down` - Graceful shutdown of all services

Doctor improvements:
- New daemon check verifies daemon is running
- Fixable with `gt doctor --fix` to auto-start daemon

The system can run degraded (any services down) but `gt up` ensures
a fully operational Gas Town with one idempotent command.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/doctor/daemon_check.go

@@ -0,0 +1,111 @@
+package doctor
+
+import (
+	"os"
+	"os/exec"
+	"time"
+
+	"github.com/steveyegge/gastown/internal/daemon"
+)
+
+// DaemonCheck verifies the daemon is running.
+type DaemonCheck struct {
+	FixableCheck
+}
+
+// NewDaemonCheck creates a new daemon check.
+func NewDaemonCheck() *DaemonCheck {
+	return &DaemonCheck{
+		FixableCheck: FixableCheck{
+			BaseCheck: BaseCheck{
+				CheckName:        "daemon",
+				CheckDescription: "Check if Gas Town daemon is running",
+			},
+		},
+	}
+}
+
+// Run checks if the daemon is running.
+func (c *DaemonCheck) Run(ctx *CheckContext) *CheckResult {
+	running, pid, err := daemon.IsRunning(ctx.TownRoot)
+	if err != nil {
+		return &CheckResult{
+			Name:    c.Name(),
+			Status:  StatusError,
+			Message: "Failed to check daemon status",
+			Details: []string{err.Error()},
+		}
+	}
+
+	if running {
+		// Get more info about daemon state
+		state, err := daemon.LoadState(ctx.TownRoot)
+		details := []string{}
+		if err == nil && !state.StartedAt.IsZero() {
+			uptime := time.Since(state.StartedAt).Round(time.Second)
+			details = append(details, "Uptime: "+uptime.String())
+			if state.HeartbeatCount > 0 {
+				details = append(details, "Heartbeats: "+string(rune(state.HeartbeatCount)))
+			}
+		}
+
+		return &CheckResult{
+			Name:    c.Name(),
+			Status:  StatusOK,
+			Message: "Daemon is running (PID " + itoa(pid) + ")",
+			Details: details,
+		}
+	}
+
+	return &CheckResult{
+		Name:    c.Name(),
+		Status:  StatusWarning,
+		Message: "Daemon is not running",
+		FixHint: "Run 'gt daemon start' or 'gt doctor --fix'",
+	}
+}
+
+// Fix starts the daemon.
+func (c *DaemonCheck) Fix(ctx *CheckContext) error {
+	// Find gt executable
+	gtPath, err := os.Executable()
+	if err != nil {
+		return err
+	}
+
+	// Start daemon in background
+	cmd := exec.Command(gtPath, "daemon", "run")
+	cmd.Dir = ctx.TownRoot
+	cmd.Stdin = nil
+	cmd.Stdout = nil
+	cmd.Stderr = nil
+
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	// Wait a moment for daemon to initialize
+	time.Sleep(300 * time.Millisecond)
+
+	return nil
+}
+
+// itoa is a simple int to string helper
+func itoa(i int) string {
+	if i == 0 {
+		return "0"
+	}
+	s := ""
+	neg := i < 0
+	if neg {
+		i = -i
+	}
+	for i > 0 {
+		s = string(rune('0'+i%10)) + s
+		i /= 10
+	}
+	if neg {
+		s = "-" + s
+	}
+	return s
+}