feat(federation): add dolt sql-server mode for daemon (bd-wkumz.2)

Add --federation flag to bd daemon start that runs dolt sql-server
instead of the embedded driver. Enables multi-writer support and
exposes remotesapi on port 8080 for peer-to-peer push/pull.

Changes:
- Add --federation flag to daemon start command
- Create dolt server manager (internal/storage/dolt/server.go)
- Update DoltStore to support server mode via MySQL protocol
- Integrate server lifecycle into daemon (auto-start/stop)
- Add tests for server management and server mode connections

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

internal/storage/dolt/server_test.go

@@ -0,0 +1,132 @@
+package dolt
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+// TestServerStartStop tests basic server lifecycle
+func TestServerStartStop(t *testing.T) {
+	// Skip if dolt is not available
+	if _, err := exec.LookPath("dolt"); err != nil {
+		t.Skip("dolt not installed, skipping server test")
+	}
+
+	// Create temp directory for test
+	tmpDir, err := os.MkdirTemp("", "dolt-server-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// Initialize dolt repo
+	cmd := exec.Command("dolt", "init")
+	cmd.Dir = tmpDir
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("failed to init dolt repo: %v, output: %s", err, output)
+	}
+	t.Logf("dolt init output: %s", output)
+
+	// Use non-standard ports to avoid conflicts
+	logFile := filepath.Join(tmpDir, "server.log")
+	server := NewServer(ServerConfig{
+		DataDir:        tmpDir,
+		SQLPort:        13306, // Non-standard port
+		RemotesAPIPort: 18080, // Non-standard port
+		Host:           "127.0.0.1",
+		LogFile:        logFile,
+	})
+
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+
+	// Start server
+	if err := server.Start(ctx); err != nil {
+		// Read log file for debugging
+		if logContent, readErr := os.ReadFile(logFile); readErr == nil {
+			t.Logf("Server log:\n%s", logContent)
+		}
+		t.Fatalf("failed to start server: %v", err)
+	}
+
+	// Verify server is running
+	if !server.IsRunning() {
+		t.Error("server should be running")
+	}
+
+	// Verify ports
+	if server.SQLPort() != 13306 {
+		t.Errorf("expected SQL port 13306, got %d", server.SQLPort())
+	}
+	if server.RemotesAPIPort() != 18080 {
+		t.Errorf("expected remotesapi port 18080, got %d", server.RemotesAPIPort())
+	}
+
+	// Verify DSN format
+	dsn := server.DSN("testdb")
+	expected := "root@tcp(127.0.0.1:13306)/testdb"
+	if dsn != expected {
+		t.Errorf("expected DSN %q, got %q", expected, dsn)
+	}
+
+	// Stop server
+	if err := server.Stop(); err != nil {
+		t.Fatalf("failed to stop server: %v", err)
+	}
+
+	// Verify server is not running
+	if server.IsRunning() {
+		t.Error("server should not be running after stop")
+	}
+}
+
+// TestServerConfigDefaults tests that config defaults are applied correctly
+func TestServerConfigDefaults(t *testing.T) {
+	server := NewServer(ServerConfig{
+		DataDir: "/tmp/test",
+	})
+
+	if server.cfg.SQLPort != DefaultSQLPort {
+		t.Errorf("expected default SQL port %d, got %d", DefaultSQLPort, server.cfg.SQLPort)
+	}
+	if server.cfg.RemotesAPIPort != DefaultRemotesAPIPort {
+		t.Errorf("expected default remotesapi port %d, got %d", DefaultRemotesAPIPort, server.cfg.RemotesAPIPort)
+	}
+	if server.cfg.Host != "127.0.0.1" {
+		t.Errorf("expected default host 127.0.0.1, got %s", server.cfg.Host)
+	}
+	if server.cfg.User != "root" {
+		t.Errorf("expected default user root, got %s", server.cfg.User)
+	}
+}
+
+// TestGetRunningServerPID tests the PID file detection
+func TestGetRunningServerPID(t *testing.T) {
+	// Create temp directory
+	tmpDir, err := os.MkdirTemp("", "dolt-pid-test-*")
+	if err != nil {
+		t.Fatalf("failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// No PID file should return 0
+	if pid := GetRunningServerPID(tmpDir); pid != 0 {
+		t.Errorf("expected 0 for non-existent PID file, got %d", pid)
+	}
+
+	// Create fake PID file with non-existent PID
+	pidFile := filepath.Join(tmpDir, "dolt-server.pid")
+	if err := os.WriteFile(pidFile, []byte("999999"), 0600); err != nil {
+		t.Fatalf("failed to write PID file: %v", err)
+	}
+
+	// Should return 0 for non-running process
+	if pid := GetRunningServerPID(tmpDir); pid != 0 {
+		t.Errorf("expected 0 for non-running process, got %d", pid)
+	}
+}