Add gt park/resume commands for async gate coordination (gt-twjr5.5)

Implements agent parking and resumption on gates:
- gt park <gate-id>: Parks work on a gate, saves context
- gt resume: Checks for cleared gates and restores work
- gt gate wake: Sends wake mail to waiters when gate closes

These commands enable agents to safely suspend work while waiting
for external conditions (timers, CI, human approval) and resume
when gates clear.

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

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

internal/cmd/gate.go

@@ -0,0 +1,186 @@
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+
+	"github.com/spf13/cobra"
+	"github.com/steveyegge/gastown/internal/mail"
+	"github.com/steveyegge/gastown/internal/style"
+	"github.com/steveyegge/gastown/internal/workspace"
+)
+
+// Gate command provides gt wrappers for gate operations.
+// Most gate commands are in beads (bd gate ...), but gt provides
+// integration with the Gas Town mail system for wake notifications.
+
+var gateCmd = &cobra.Command{
+	Use:     "gate",
+	GroupID: GroupWork,
+	Short:   "Gate coordination commands",
+	Long: `Gate commands for async coordination.
+
+Most gate commands are in beads:
+  bd gate create   - Create a gate (timer, gh:run, human, mail)
+  bd gate show     - Show gate details
+  bd gate list     - List open gates
+  bd gate close    - Close a gate
+  bd gate approve  - Approve a human gate
+  bd gate eval     - Evaluate and close elapsed gates
+
+The gt gate command provides Gas Town integration:
+  gt gate wake     - Send wake mail to gate waiters after close`,
+}
+
+var gateWakeCmd = &cobra.Command{
+	Use:   "wake <gate-id>",
+	Short: "Send wake mail to gate waiters",
+	Long: `Send wake mail to all waiters on a gate.
+
+This command should be called after a gate closes to notify waiting agents.
+Typically called by Deacon after 'bd gate eval' or after manual gate close.
+
+The wake mail includes:
+  - Gate ID and close reason
+  - Instructions to run 'gt resume'
+
+Examples:
+  # After manual gate close
+  bd gate close gt-xxx --reason "Approved"
+  gt gate wake gt-xxx
+
+  # In Deacon patrol after gate eval
+  for gate in $(bd gate eval --json | jq -r '.closed[]'); do
+    gt gate wake $gate
+  done`,
+	Args: cobra.ExactArgs(1),
+	RunE: runGateWake,
+}
+
+var (
+	gateWakeJSON   bool
+	gateWakeDryRun bool
+)
+
+func init() {
+	gateWakeCmd.Flags().BoolVar(&gateWakeJSON, "json", false, "Output as JSON")
+	gateWakeCmd.Flags().BoolVarP(&gateWakeDryRun, "dry-run", "n", false, "Show what would be done")
+
+	gateCmd.AddCommand(gateWakeCmd)
+	rootCmd.AddCommand(gateCmd)
+}
+
+// GateWakeResult represents the result of sending wake mail.
+type GateWakeResult struct {
+	GateID      string   `json:"gate_id"`
+	CloseReason string   `json:"close_reason"`
+	Waiters     []string `json:"waiters"`
+	Notified    []string `json:"notified"`
+	Failed      []string `json:"failed,omitempty"`
+}
+
+func runGateWake(cmd *cobra.Command, args []string) error {
+	gateID := args[0]
+
+	// Get gate info
+	gateCheck := exec.Command("bd", "gate", "show", gateID, "--json")
+	gateOutput, err := gateCheck.Output()
+	if err != nil {
+		return fmt.Errorf("gate '%s' not found or not accessible", gateID)
+	}
+
+	var gateInfo struct {
+		ID          string   `json:"id"`
+		Status      string   `json:"status"`
+		CloseReason string   `json:"close_reason"`
+		Waiters     []string `json:"waiters"`
+	}
+	if err := json.Unmarshal(gateOutput, &gateInfo); err != nil {
+		return fmt.Errorf("parsing gate info: %w", err)
+	}
+
+	if gateInfo.Status != "closed" {
+		return fmt.Errorf("gate '%s' is not closed (status: %s) - wake mail only sent for closed gates", gateID, gateInfo.Status)
+	}
+
+	if len(gateInfo.Waiters) == 0 {
+		if gateWakeJSON {
+			result := GateWakeResult{
+				GateID:      gateID,
+				CloseReason: gateInfo.CloseReason,
+				Waiters:     []string{},
+				Notified:    []string{},
+			}
+			return outputGateWakeResult(result)
+		}
+		fmt.Printf("%s Gate %s has no waiters to notify\n", style.Dim.Render("○"), gateID)
+		return nil
+	}
+
+	if gateWakeDryRun {
+		fmt.Printf("Would send wake mail for gate %s to:\n", gateID)
+		for _, w := range gateInfo.Waiters {
+			fmt.Printf("  - %s\n", w)
+		}
+		return nil
+	}
+
+	// Find town root for mail routing
+	townRoot, err := workspace.FindFromCwd()
+	if err != nil {
+		return fmt.Errorf("finding town root: %w", err)
+	}
+
+	router := mail.NewRouter(townRoot)
+
+	result := GateWakeResult{
+		GateID:      gateID,
+		CloseReason: gateInfo.CloseReason,
+		Waiters:     gateInfo.Waiters,
+		Notified:    []string{},
+		Failed:      []string{},
+	}
+
+	subject := fmt.Sprintf("🚦 GATE CLEARED: %s", gateID)
+	body := fmt.Sprintf("Gate %s has closed.\n\nReason: %s\n\nRun 'gt resume' to continue your parked work.",
+		gateID, gateInfo.CloseReason)
+
+	for _, waiter := range gateInfo.Waiters {
+		msg := &mail.Message{
+			From:     "deacon/",
+			To:       waiter,
+			Subject:  subject,
+			Body:     body,
+			Type:     mail.TypeNotification,
+			Priority: mail.PriorityHigh,
+			Wisp:     true,
+		}
+		if err := router.Send(msg); err != nil {
+			result.Failed = append(result.Failed, waiter)
+		} else {
+			result.Notified = append(result.Notified, waiter)
+		}
+	}
+
+	if gateWakeJSON {
+		return outputGateWakeResult(result)
+	}
+
+	fmt.Printf("%s Sent wake mail for gate %s\n", style.Bold.Render("🚦"), gateID)
+	if len(result.Notified) > 0 {
+		fmt.Printf("  Notified: %v\n", result.Notified)
+	}
+	if len(result.Failed) > 0 {
+		fmt.Printf("  Failed: %v\n", result.Failed)
+	}
+
+	return nil
+}
+
+func outputGateWakeResult(result GateWakeResult) error {
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
+	return enc.Encode(result)
+}