feat: add SwarmManager for swarm lifecycle operations

- Create/Start/Cancel swarm lifecycle methods
- State transition validation (Created->Active->Merging->Landed)
- Task assignment and state tracking
- GetReadyTasks/GetActiveTasks queries
- IsComplete check for swarm completion
- Integration with beads CLI for task loading

Closes gt-kmn.2

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

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

internal/swarm/manager_test.go

@@ -0,0 +1,187 @@
+package swarm
+
+import (
+	"testing"
+
+	"github.com/steveyegge/gastown/internal/rig"
+)
+
+func TestManagerCreate(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	swarm, err := m.Create("epic-1", []string{"Toast", "Nux"}, "main")
+	if err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+
+	if swarm.ID != "epic-1" {
+		t.Errorf("ID = %q, want %q", swarm.ID, "epic-1")
+	}
+	if swarm.State != SwarmCreated {
+		t.Errorf("State = %q, want %q", swarm.State, SwarmCreated)
+	}
+	if len(swarm.Workers) != 2 {
+		t.Errorf("Workers = %d, want 2", len(swarm.Workers))
+	}
+}
+
+func TestManagerCreateDuplicate(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	_, err := m.Create("epic-1", []string{"Toast"}, "main")
+	if err != nil {
+		t.Fatalf("First Create failed: %v", err)
+	}
+
+	_, err = m.Create("epic-1", []string{"Nux"}, "main")
+	if err != ErrSwarmExists {
+		t.Errorf("Create duplicate = %v, want ErrSwarmExists", err)
+	}
+}
+
+func TestManagerStateTransitions(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	swarm, _ := m.Create("epic-1", []string{"Toast"}, "main")
+
+	// Start
+	if err := m.Start(swarm.ID); err != nil {
+		t.Errorf("Start failed: %v", err)
+	}
+	s, _ := m.GetSwarm(swarm.ID)
+	if s.State != SwarmActive {
+		t.Errorf("State after Start = %q, want %q", s.State, SwarmActive)
+	}
+
+	// Can't start again
+	if err := m.Start(swarm.ID); err == nil {
+		t.Error("Start from Active should fail")
+	}
+
+	// Transition to Merging
+	if err := m.UpdateState(swarm.ID, SwarmMerging); err != nil {
+		t.Errorf("UpdateState to Merging failed: %v", err)
+	}
+
+	// Transition to Landed
+	if err := m.UpdateState(swarm.ID, SwarmLanded); err != nil {
+		t.Errorf("UpdateState to Landed failed: %v", err)
+	}
+
+	// Can't transition from terminal
+	if err := m.UpdateState(swarm.ID, SwarmActive); err == nil {
+		t.Error("UpdateState from Landed should fail")
+	}
+}
+
+func TestManagerCancel(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	swarm, _ := m.Create("epic-1", []string{"Toast"}, "main")
+	m.Start(swarm.ID)
+
+	if err := m.Cancel(swarm.ID, "user requested"); err != nil {
+		t.Errorf("Cancel failed: %v", err)
+	}
+
+	s, _ := m.GetSwarm(swarm.ID)
+	if s.State != SwarmCancelled {
+		t.Errorf("State after Cancel = %q, want %q", s.State, SwarmCancelled)
+	}
+	if s.Error != "user requested" {
+		t.Errorf("Error = %q, want %q", s.Error, "user requested")
+	}
+}
+
+func TestManagerTaskOperations(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	swarm, _ := m.Create("epic-1", []string{"Toast"}, "main")
+
+	// Manually add tasks (normally loaded from beads)
+	swarm.Tasks = []SwarmTask{
+		{IssueID: "task-1", Title: "Task 1", State: TaskPending},
+		{IssueID: "task-2", Title: "Task 2", State: TaskPending},
+	}
+
+	// Get ready tasks
+	ready, err := m.GetReadyTasks(swarm.ID)
+	if err != nil {
+		t.Errorf("GetReadyTasks failed: %v", err)
+	}
+	if len(ready) != 2 {
+		t.Errorf("GetReadyTasks = %d, want 2", len(ready))
+	}
+
+	// Assign task
+	if err := m.AssignTask(swarm.ID, "task-1", "Toast"); err != nil {
+		t.Errorf("AssignTask failed: %v", err)
+	}
+
+	// Check assignment
+	s, _ := m.GetSwarm(swarm.ID)
+	if s.Tasks[0].Assignee != "Toast" {
+		t.Errorf("Assignee = %q, want %q", s.Tasks[0].Assignee, "Toast")
+	}
+	if s.Tasks[0].State != TaskAssigned {
+		t.Errorf("State = %q, want %q", s.Tasks[0].State, TaskAssigned)
+	}
+
+	// Update state
+	if err := m.UpdateTaskState(swarm.ID, "task-1", TaskMerged); err != nil {
+		t.Errorf("UpdateTaskState failed: %v", err)
+	}
+	s, _ = m.GetSwarm(swarm.ID)
+	if s.Tasks[0].State != TaskMerged {
+		t.Errorf("State = %q, want %q", s.Tasks[0].State, TaskMerged)
+	}
+	if s.Tasks[0].MergedAt == nil {
+		t.Error("MergedAt should be set")
+	}
+}
+
+func TestManagerIsComplete(t *testing.T) {
+	r := &rig.Rig{
+		Name: "test-rig",
+		Path: "/tmp/test-rig",
+	}
+	m := NewManager(r)
+
+	swarm, _ := m.Create("epic-1", []string{"Toast"}, "main")
+	swarm.Tasks = []SwarmTask{
+		{IssueID: "task-1", State: TaskPending},
+		{IssueID: "task-2", State: TaskMerged},
+	}
+
+	complete, _ := m.IsComplete(swarm.ID)
+	if complete {
+		t.Error("IsComplete should be false with pending task")
+	}
+
+	// Complete the pending task
+	m.UpdateTaskState(swarm.ID, "task-1", TaskMerged)
+	complete, _ = m.IsComplete(swarm.ID)
+	if !complete {
+		t.Error("IsComplete should be true when all tasks merged")
+	}
+}