fix(build): add CGO build constraints for Dolt-dependent files

The dolthub/gozstd dependency requires CGO. Several files were importing
the dolt package without build constraints, causing CI failures when
building with CGO_ENABLED=0 for Linux, FreeBSD, and Android.

Changes:
- Add //go:build cgo to federation.go and doctor/federation.go
- Create dolt_server_cgo.go/nocgo.go to abstract dolt.Server usage
- Create federation_nocgo.go with stub command explaining CGO requirement
- Create doctor/federation_nocgo.go with stub health checks
- Update daemon.go to use the dolt server abstraction

Federation and Dolt-specific features are unavailable in non-CGO builds.
Users are directed to pre-built binaries from GitHub releases.

Fixes v0.49.0 CI failure.

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

cmd/bd/daemon.go

@@ -17,7 +17,6 @@ import (
 	"github.com/steveyegge/beads/internal/configfile"
 	"github.com/steveyegge/beads/internal/daemon"
 	"github.com/steveyegge/beads/internal/rpc"
-	"github.com/steveyegge/beads/internal/storage/dolt"
 	"github.com/steveyegge/beads/internal/storage/factory"
 	"github.com/steveyegge/beads/internal/storage/sqlite"
 	"github.com/steveyegge/beads/internal/syncbranch"
@@ -421,13 +420,17 @@ func runDaemonLoop(interval time.Duration, autoCommit, autoPush, autoPull, local
 	}
 
 	// Start dolt sql-server if federation mode is enabled and backend is dolt
-	var doltServer *dolt.Server
+	var doltServer *DoltServerHandle
 	factoryOpts := factory.Options{}
 	if federation && backend != configfile.BackendDolt {
 		log.Warn("federation mode requires dolt backend, ignoring --federation flag")
 		federation = false
 	}
 	if federation && backend == configfile.BackendDolt {
+		if !DoltServerAvailable() {
+			log.Error("federation mode requires CGO; use pre-built binaries from GitHub releases")
+			return
+		}
 		log.Info("starting dolt sql-server for federation mode")
 
 		doltPath := filepath.Join(beadsDir, "dolt")
@@ -436,22 +439,16 @@ func runDaemonLoop(interval time.Duration, autoCommit, autoPush, autoPull, local
 		// Use provided ports or defaults
 		sqlPort := federationPort
 		if sqlPort == 0 {
-			sqlPort = dolt.DefaultSQLPort
+			sqlPort = DoltDefaultSQLPort
 		}
 		remotePort := remotesapiPort
 		if remotePort == 0 {
-			remotePort = dolt.DefaultRemotesAPIPort
+			remotePort = DoltDefaultRemotesAPIPort
 		}
 
-		doltServer = dolt.NewServer(dolt.ServerConfig{
-			DataDir:        doltPath,
-			SQLPort:        sqlPort,
-			RemotesAPIPort: remotePort,
-			Host:           "127.0.0.1",
-			LogFile:        serverLogFile,
-		})
-
-		if err := doltServer.Start(ctx); err != nil {
+		var err error
+		doltServer, err = StartDoltServer(ctx, doltPath, serverLogFile, sqlPort, remotePort)
+		if err != nil {
 			log.Error("failed to start dolt sql-server", "error", err)
 			return
 		}

cmd/bd/doctor/federation.go

@@ -1,3 +1,5 @@
+//go:build cgo
+
 package doctor
 
 import (

cmd/bd/doctor/federation_nocgo.go

@@ -0,0 +1,53 @@
+//go:build !cgo
+
+package doctor
+
+// CheckFederationRemotesAPI returns N/A when CGO is not available.
+func CheckFederationRemotesAPI(path string) DoctorCheck {
+	return DoctorCheck{
+		Name:     "Federation remotesapi",
+		Status:   StatusOK,
+		Message:  "N/A (requires CGO)",
+		Category: CategoryFederation,
+	}
+}
+
+// CheckFederationPeerConnectivity returns N/A when CGO is not available.
+func CheckFederationPeerConnectivity(path string) DoctorCheck {
+	return DoctorCheck{
+		Name:     "Peer Connectivity",
+		Status:   StatusOK,
+		Message:  "N/A (requires CGO)",
+		Category: CategoryFederation,
+	}
+}
+
+// CheckFederationSyncStaleness returns N/A when CGO is not available.
+func CheckFederationSyncStaleness(path string) DoctorCheck {
+	return DoctorCheck{
+		Name:     "Sync Staleness",
+		Status:   StatusOK,
+		Message:  "N/A (requires CGO)",
+		Category: CategoryFederation,
+	}
+}
+
+// CheckFederationConflicts returns N/A when CGO is not available.
+func CheckFederationConflicts(path string) DoctorCheck {
+	return DoctorCheck{
+		Name:     "Federation Conflicts",
+		Status:   StatusOK,
+		Message:  "N/A (requires CGO)",
+		Category: CategoryFederation,
+	}
+}
+
+// CheckDoltServerModeMismatch returns N/A when CGO is not available.
+func CheckDoltServerModeMismatch(path string) DoctorCheck {
+	return DoctorCheck{
+		Name:     "Dolt Mode",
+		Status:   StatusOK,
+		Message:  "N/A (requires CGO)",
+		Category: CategoryFederation,
+	}
+}

cmd/bd/dolt_server_cgo.go

@@ -0,0 +1,74 @@
+//go:build cgo
+
+package main
+
+import (
+	"context"
+
+	"github.com/steveyegge/beads/internal/storage/dolt"
+)
+
+// DoltServerHandle wraps a dolt.Server for CGO builds
+type DoltServerHandle struct {
+	server *dolt.Server
+}
+
+// DoltDefaultSQLPort is the default SQL port for dolt server
+const DoltDefaultSQLPort = dolt.DefaultSQLPort
+
+// DoltDefaultRemotesAPIPort is the default remotesapi port for dolt server
+const DoltDefaultRemotesAPIPort = dolt.DefaultRemotesAPIPort
+
+// StartDoltServer starts a dolt sql-server for federation mode
+func StartDoltServer(ctx context.Context, dataDir, logFile string, sqlPort, remotePort int) (*DoltServerHandle, error) {
+	server := dolt.NewServer(dolt.ServerConfig{
+		DataDir:        dataDir,
+		SQLPort:        sqlPort,
+		RemotesAPIPort: remotePort,
+		Host:           "127.0.0.1",
+		LogFile:        logFile,
+	})
+
+	if err := server.Start(ctx); err != nil {
+		return nil, err
+	}
+
+	return &DoltServerHandle{server: server}, nil
+}
+
+// Stop stops the dolt server
+func (h *DoltServerHandle) Stop() error {
+	if h.server != nil {
+		return h.server.Stop()
+	}
+	return nil
+}
+
+// SQLPort returns the SQL port the server is listening on
+func (h *DoltServerHandle) SQLPort() int {
+	if h.server != nil {
+		return h.server.SQLPort()
+	}
+	return 0
+}
+
+// RemotesAPIPort returns the remotesapi port the server is listening on
+func (h *DoltServerHandle) RemotesAPIPort() int {
+	if h.server != nil {
+		return h.server.RemotesAPIPort()
+	}
+	return 0
+}
+
+// Host returns the host the server is listening on
+func (h *DoltServerHandle) Host() string {
+	if h.server != nil {
+		return h.server.Host()
+	}
+	return ""
+}
+
+// DoltServerAvailable returns true when CGO is available
+func DoltServerAvailable() bool {
+	return true
+}

cmd/bd/dolt_server_nocgo.go

@@ -0,0 +1,50 @@
+//go:build !cgo
+
+package main
+
+import (
+	"context"
+	"errors"
+)
+
+// DoltServerHandle is a stub for non-CGO builds
+type DoltServerHandle struct{}
+
+// DoltDefaultSQLPort is the default SQL port for dolt server
+const DoltDefaultSQLPort = 3306
+
+// DoltDefaultRemotesAPIPort is the default remotesapi port for dolt server
+const DoltDefaultRemotesAPIPort = 50051
+
+// ErrDoltRequiresCGO is returned when dolt features are requested without CGO
+var ErrDoltRequiresCGO = errors.New("dolt backend requires CGO; use pre-built binaries from GitHub releases or enable CGO")
+
+// StartDoltServer returns an error in non-CGO builds
+func StartDoltServer(ctx context.Context, dataDir, logFile string, sqlPort, remotePort int) (*DoltServerHandle, error) {
+	return nil, ErrDoltRequiresCGO
+}
+
+// Stop is a no-op stub
+func (h *DoltServerHandle) Stop() error {
+	return nil
+}
+
+// SQLPort returns 0 in non-CGO builds
+func (h *DoltServerHandle) SQLPort() int {
+	return 0
+}
+
+// RemotesAPIPort returns 0 in non-CGO builds
+func (h *DoltServerHandle) RemotesAPIPort() int {
+	return 0
+}
+
+// Host returns empty string in non-CGO builds
+func (h *DoltServerHandle) Host() string {
+	return ""
+}
+
+// DoltServerAvailable returns false when CGO is not available
+func DoltServerAvailable() bool {
+	return false
+}

cmd/bd/federation.go

@@ -1,3 +1,5 @@
+//go:build cgo
+
 package main
 
 import (

cmd/bd/federation_nocgo.go

@@ -0,0 +1,34 @@
+//go:build !cgo
+
+package main
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+var federationCmd = &cobra.Command{
+	Use:     "federation",
+	GroupID: "sync",
+	Short:   "Manage peer-to-peer federation (requires CGO)",
+	Long: `Federation commands require CGO and the Dolt storage backend.
+
+This binary was built without CGO support. To use federation features:
+  1. Use pre-built binaries from GitHub releases, or
+  2. Build from source with CGO enabled
+
+Federation enables synchronized issue tracking across multiple Gas Towns,
+each maintaining their own Dolt database while sharing updates via remotes.`,
+	Run: func(cmd *cobra.Command, args []string) {
+		fmt.Println("Federation requires CGO and Dolt backend.")
+		fmt.Println("")
+		fmt.Println("This binary was built without CGO support. To use federation:")
+		fmt.Println("  1. Download pre-built binaries from GitHub releases")
+		fmt.Println("  2. Or build from source with CGO enabled")
+	},
+}
+
+func init() {
+	rootCmd.AddCommand(federationCmd)
+}