* fix(onebot): add metadata for direct and group message handling
* fix(qq): add metadata for direct and group message handling
* fix(dingtalk): add metadata for direct and group message handling
* fix(feishu): add metadata for direct and group message handling
* fix(whatsapp): add metadata for direct and group message handlinga
* fix(line): add metadata for direct and group message handling
* fix(maixcam): add metadata for person detection handling
* fix(config): add default session configuration with DMScope
Multiple packages had their own private truncate implementations:
- channels/telegram.go: truncateString (byte-based, no "...")
- channels/dingtalk.go: truncateStringDingTalk (byte-based, no "...")
- voice/transcriber.go: truncateText (byte-based, with "...")
All three are functionally equivalent to the existing utils.Truncate,
which already handles rune-safe truncation and appends "..." correctly.
Replace all private copies with utils.Truncate and delete the dead code.
