fix(savedata): write playtime back to binary blob on save

updateSaveDataWithStruct only wrote RP and KQF into the blob, leaving
the playtime field stale. On each reconnect, GetCharacterSaveData read
the old in-game counter from the blob and reset s.playtime to it,
rolling back all progress accumulated during the previous session.

Playtime is now persisted into the blob alongside RP, using the same
S6 mode guard as the read path in updateStructWithSaveData.

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed playtime regression across sessions: `updateSaveDataWithStruct` now writes the accumulated playtime back into the binary save blob, preventing each reconnect from loading a stale in-game counter and rolling back progress.
+
 ## [9.3.1] - 2026-03-23
 
 ### Added

server/channelserver/model_character.go

@@ -148,6 +148,11 @@ func (save *CharacterSaveData) updateSaveDataWithStruct() {
 	if save.Mode >= cfg.F4 {
 		copy(save.decompSave[save.Pointers[pRP]:save.Pointers[pRP]+saveFieldRP], rpBytes)
 	}
+	if save.Mode >= cfg.S6 {
+		playtimeBytes := make([]byte, 4)
+		binary.LittleEndian.PutUint32(playtimeBytes, save.Playtime)
+		copy(save.decompSave[save.Pointers[pPlaytime]:save.Pointers[pPlaytime]+saveFieldPlaytime], playtimeBytes)
+	}
 	if save.Mode >= cfg.G10 {
 		copy(save.decompSave[save.Pointers[pKQF]:save.Pointers[pKQF]+saveFieldKQF], save.KQF)
 	}