Network tab: Router rows show blank RSSI/LQI and static/zero TX retry/parent deltas

[DarinShapiro]

Summary

In the network-tab view, routing devices frequently display blank values for RSSI/LQI and zero counts for TX retry and Parent Δ 24h. This leads to an impression of broken data even when the backend is operating as currently designed.

Repro

1. Open the Network dashboard.
2. Observe rows for 'Router' or 'Leader' class nodes.
3. Note that RSSI, LQI, and delta fields are often empty or zero.

Actual

• RSSI/LQI columns are blank for most routers.
• Parent Δ 24h is 0 or '-' for routers.
• TX retry 1h is 0 for routers even under load.

Expected

• Informative signal metrics for all nodes where neighbor data exists.
• Clear indication that Parent Δ is specific to sleepy/end-devices if not applicable to routers.
• Meaningful TX retry deltas.

Diagnosis

Based on the codebase analysis:

• RSSI/LQI:
  odes.get_latest_signal_strength derives these values only from incoming links where
  eighbor_eui64 matches the node. Consequently, routers only show values if a peer specifically reports them in a link set.
• Parent Δ 24h: The dashboard renders this from parent_change_count. While device_discovery comments describe this as a stability signal for sleepy/end-devices, it is currently shown for all nodes, appearing as a '0' for routers which naturally don't change parents the same way.
• TX retry 1h: This comes from /v1/counters/deltas. It reflects last-minus-first counter movement. For routers, if the counters are flat or not being sampled at the right granularity, the delta remains 0.

Notes

The net result is that router-class rows frequently look broken or uninformative. This is adjacent to, but distinct from, the issue described in #91.

[DarinShapiro]

Commit 96f7572 improves router RSSI/LQI fallback from reporter-owned link rows and renders Parent Δ as not applicable for router-class nodes. Note that TX retry delta granularity is still open.