feat: implement history split functionality to optimize context usage and add corresponding UI settings

internal/config/codec.go

@@ -51,6 +51,9 @@ func (c Config) MarshalJSON() ([]byte, error) {
 		m["embeddings"] = c.Embeddings
 	}
 	m["auto_delete"] = c.AutoDelete
+	if c.HistorySplit.Enabled != nil || c.HistorySplit.TriggerAfterTurns != nil {
+		m["history_split"] = c.HistorySplit
+	}
 	if c.VercelSyncHash != "" {
 		m["_vercel_sync_hash"] = c.VercelSyncHash
 	}
@@ -122,6 +125,10 @@ func (c *Config) UnmarshalJSON(b []byte) error {
 			if err := json.Unmarshal(v, &c.AutoDelete); err != nil {
 				return fmt.Errorf("invalid field %q: %w", k, err)
 			}
+		case "history_split":
+			if err := json.Unmarshal(v, &c.HistorySplit); err != nil {
+				return fmt.Errorf("invalid field %q: %w", k, err)
+			}
 		case "_vercel_sync_hash":
 			if err := json.Unmarshal(v, &c.VercelSyncHash); err != nil {
 				return fmt.Errorf("invalid field %q: %w", k, err)
@@ -156,9 +163,13 @@ func (c Config) Clone() Config {
 			WideInputStrictOutput: cloneBoolPtr(c.Compat.WideInputStrictOutput),
 			StripReferenceMarkers: cloneBoolPtr(c.Compat.StripReferenceMarkers),
 		},
-		Responses:        c.Responses,
-		Embeddings:       c.Embeddings,
-		AutoDelete:       c.AutoDelete,
+		Responses:  c.Responses,
+		Embeddings: c.Embeddings,
+		AutoDelete: c.AutoDelete,
+		HistorySplit: HistorySplitConfig{
+			Enabled:           cloneBoolPtr(c.HistorySplit.Enabled),
+			TriggerAfterTurns: cloneIntPtr(c.HistorySplit.TriggerAfterTurns),
+		},
 		VercelSyncHash:   c.VercelSyncHash,
 		VercelSyncTime:   c.VercelSyncTime,
 		AdditionalFields: map[string]any{},
@@ -188,6 +199,14 @@ func cloneBoolPtr(in *bool) *bool {
 	return &v
 }
 
+func cloneIntPtr(in *int) *int {
+	if in == nil {
+		return nil
+	}
+	v := *in
+	return &v
+}
+
 func parseConfigString(raw string) (Config, error) {
 	var cfg Config
 	candidates := []string{raw}