feat(vault): chat_id isolation for isolated teams

- Add vault_documents.chat_id + composite index (migration 000056)
- Filter vault_search by chat_id when team.workspace_scope=isolated
- Stamp chat_id on AfterWrite/AfterWriteMedia for isolated teams
- Deny cross-chat vault_read in isolated teams (M2 fix)
- RunContext.TeamIsolated flag resolved once per run
- Fallback WorkspaceChatID → ChatID in loop_context for entry points
  that don't set WorkspaceChatID explicitly (WS direct, HTTP, cron)

Fixes cross-chat doc leak where agent in chat A could see vault docs
from chat B within the same isolated team.

cmd/gateway_consumer_normal.go

@@ -389,6 +389,7 @@ func processNormalMessage(
 		ChannelType:       resolveChannelType(deps.ChannelMgr, msg.Channel),
 		ChatTitle:         msg.Metadata[tools.MetaChatTitle],
 		ChatID:            msg.ChatID,
+		WorkspaceChatID:   msg.ChatID,
 		PeerKind:          peerKind,
 		LocalKey:          msg.Metadata["local_key"],
 		UserID:            userID,