fix: resolve CodeRabbit findings — init ordering, crash safety, lock order

- log.go: remove atomic.Pointer — defaultLog init was nil (var runs before init())
- error.go: Reports(n) validates n<=0, appendReport creates parent dir
- contract.go: WithServiceLock is order-independent (LockApply after all opts)

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/core/contract.go

@@ -106,6 +106,7 @@ func New(opts ...Option) (*Core, error) {
 		}
 	}
 
+	c.LockApply()
 	return c, nil
 }
 
@@ -188,10 +189,10 @@ func WithAssets(efs embed.FS) Option {
 
 
 // WithServiceLock prevents service registration after initialisation.
+// Order-independent — lock is applied after all options are processed.
 func WithServiceLock() Option {
 	return func(c *Core) error {
 		c.LockEnable()
-		c.LockApply()
 		return nil
 	}
 }

pkg/core/error.go

@@ -13,6 +13,7 @@ import (
 	"iter"
 	"maps"
 	"os"
+	"path/filepath"
 	"runtime"
 	"runtime/debug"
 	"strings"
@@ -385,7 +386,7 @@ func (h *ErrPan) Reports(n int) ([]CrashReport, error) {
 	if err := json.Unmarshal(data, &reports); err != nil {
 		return nil, err
 	}
-	if len(reports) <= n {
+	if n <= 0 || len(reports) <= n {
 		return reports, nil
 	}
 	return reports[len(reports)-n:], nil
@@ -406,6 +407,7 @@ func (h *ErrPan) appendReport(report CrashReport) {
 
 	reports = append(reports, report)
 	if data, err := json.MarshalIndent(reports, "", "  "); err == nil {
+		_ = os.MkdirAll(filepath.Dir(h.filePath), 0755)
 		_ = os.WriteFile(h.filePath, data, 0600)
 	}
 }

pkg/core/log.go

@@ -12,7 +12,6 @@ import (
 	"os/user"
 	"slices"
 	"sync"
-	"sync/atomic"
 	"time"
 )
 
@@ -298,23 +297,16 @@ func Username() string {
 
 // --- Default logger ---
 
-var defaultLogPtr atomic.Pointer[Log]
-
-func init() {
-	l := NewLog(LogOpts{Level: LevelInfo})
-	defaultLogPtr.Store(l)
-}
-
-var defaultLog = defaultLogPtr.Load()
+var defaultLog = NewLog(LogOpts{Level: LevelInfo})
 
 // Default returns the default logger.
 func Default() *Log {
-	return defaultLogPtr.Load()
+	return defaultLog
 }
 
-// SetDefault sets the default logger (thread-safe).
+// SetDefault sets the default logger.
 func SetDefault(l *Log) {
-	defaultLogPtr.Store(l)
+	defaultLog = l
 }
 
 // SetLevel sets the default logger's level.