fix: SenderName/WasMentioned missing in DMWork adapter inbound context

[yujiawei]

Problem

DMWork adapter only sets SenderId: message.from_uid in finalizeInboundContext. The AI has no idea who is talking — it only sees a raw UID.

Missing OpenClaw SDK fields

• SenderName — display name
• SenderUsername — username fallback
• WasMentioned — framework can't gate elevated/exec permissions properly

Root cause

WuKongIM RECV binary protocol only pushes from_uid, no sender name. The adapter had uidToNameMap available from group member cache but never used it to populate these fields.

Additional issues found

1. Reply from_name and MultipleForward users[].name data was received but not cached
2. Group members not preloaded on startup (empty uidToNameMap until first group message)
3. cleanupStaleCaches bug: _uidToNameMaps.delete(groupId) on flat uid→name map
4. DM cross-space users unresolvable (different uid prefix per space)

Fix

PR #141 addresses all issues above.

Remaining gap

Pure DM users (never appeared in any group) need backend /v1/bot/user/info API.