The display filter `gsm_a.tmsi || e212.imsi` was too restrictive —
paging requests use different field paths for TMSI so nothing matched.
The capture filter (-f 'udp port 4729') already limits to GSMTAP, and
the parser discards rows without TMSI/IMSI identifiers.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>