feat(daemons): implement discovery and list command (bd-146, bd-147)

- Add daemon discovery mechanism with socket scanning
- Implement depth-limited filesystem walk to avoid hangs
- Add DaemonInfo struct with metadata collection
- Create 'bd daemons list' command with table and JSON output
- Add FindDaemonByWorkspace and CleanupStaleSockets utilities
- Fix workspace path to be parent of .beads directory
- Add comprehensive tests for discovery functionality

Closes bd-146
Closes bd-147

internal/daemon/discovery_test.go

@@ -0,0 +1,117 @@
+package daemon
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/steveyegge/beads/internal/rpc"
+	"github.com/steveyegge/beads/internal/storage/sqlite"
+)
+
+func TestDiscoverDaemon(t *testing.T) {
+	tmpDir := t.TempDir()
+	workspace := filepath.Join(tmpDir, ".beads")
+	os.MkdirAll(workspace, 0755)
+
+	// Start daemon
+	dbPath := filepath.Join(workspace, "test.db")
+	socketPath := filepath.Join(workspace, "bd.sock")
+	store, err := sqlite.New(dbPath)
+	if err != nil {
+		t.Fatalf("failed to create storage: %v", err)
+	}
+	defer store.Close()
+
+	server := rpc.NewServer(socketPath, store, tmpDir, dbPath)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go server.Start(ctx)
+	<-server.WaitReady()
+	defer server.Stop()
+
+	// Test discoverDaemon directly
+	daemon := discoverDaemon(socketPath)
+	if !daemon.Alive {
+		t.Errorf("daemon not alive: %s", daemon.Error)
+	}
+	if daemon.PID != os.Getpid() {
+		t.Errorf("wrong PID: expected %d, got %d", os.Getpid(), daemon.PID)
+	}
+	if daemon.UptimeSeconds <= 0 {
+		t.Errorf("invalid uptime: %f", daemon.UptimeSeconds)
+	}
+	if daemon.WorkspacePath != tmpDir {
+		t.Errorf("wrong workspace: expected %s, got %s", tmpDir, daemon.WorkspacePath)
+	}
+}
+
+func TestFindDaemonByWorkspace(t *testing.T) {
+	tmpDir := t.TempDir()
+	workspace := filepath.Join(tmpDir, ".beads")
+	os.MkdirAll(workspace, 0755)
+
+	// Start daemon
+	dbPath := filepath.Join(workspace, "test.db")
+	socketPath := filepath.Join(workspace, "bd.sock")
+	store, err := sqlite.New(dbPath)
+	if err != nil {
+		t.Fatalf("failed to create storage: %v", err)
+	}
+	defer store.Close()
+
+	server := rpc.NewServer(socketPath, store, tmpDir, dbPath)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	go server.Start(ctx)
+	<-server.WaitReady()
+	defer server.Stop()
+
+	// Find daemon by workspace
+	daemon, err := FindDaemonByWorkspace(tmpDir)
+	if err != nil {
+		t.Fatalf("failed to find daemon: %v", err)
+	}
+	if daemon == nil {
+		t.Fatal("daemon not found")
+	}
+	if !daemon.Alive {
+		t.Errorf("daemon not alive: %s", daemon.Error)
+	}
+	if daemon.WorkspacePath != tmpDir {
+		t.Errorf("wrong workspace: expected %s, got %s", tmpDir, daemon.WorkspacePath)
+	}
+}
+
+func TestCleanupStaleSockets(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	// Create stale socket file
+	stalePath := filepath.Join(tmpDir, "stale.sock")
+	if err := os.WriteFile(stalePath, []byte{}, 0644); err != nil {
+		t.Fatalf("failed to create stale socket: %v", err)
+	}
+
+	daemons := []DaemonInfo{
+		{
+			SocketPath: stalePath,
+			Alive:      false,
+		},
+	}
+
+	cleaned, err := CleanupStaleSockets(daemons)
+	if err != nil {
+		t.Fatalf("cleanup failed: %v", err)
+	}
+	if cleaned != 1 {
+		t.Errorf("expected 1 cleaned, got %d", cleaned)
+	}
+
+	// Verify socket was removed
+	if _, err := os.Stat(stalePath); !os.IsNotExist(err) {
+		t.Error("stale socket still exists")
+	}
+}