VAPI-4167 feat: per-peer sent/received counters in call stats

[smoghe-bw]

Jira: VAPI-4167

Summary

• Add publishPeer and subscribePeer (new exported PeerCallStats type) to CallStatsSnapshot.
• Each holds audio RTP packetsSent, bytesSent, packetsReceived, bytesReceived, read only from that peer connection's own stats report, so stats can be attributed to the peer they came from.
• The publish peer normally only sends and the subscribe peer normally only receives; the other direction is normally 0.
• Non-breaking: every existing flat field keeps its meaning and value (flat bytesSent is still publish outbound, flat bytesReceived is still subscribe inbound, bitrates unchanged).
• README getCallStats section documents the new fields.

Example snapshot fragment:

{
  "packetsReceived": 10,
  "bytesReceived": 2000,
  "packetsSent": 20,
  "bytesSent": 4000,
  "publishPeer": { "packetsSent": 20, "bytesSent": 4000, "packetsReceived": 0, "bytesReceived": 0 },
  "subscribePeer": { "packetsSent": 0, "bytesSent": 0, "packetsReceived": 10, "bytesReceived": 2000 }
}

Test plan

• npm test passes (180 tests)
• Each peer's counters come only from its own report (distinct numbers for outbound and inbound on both reports)
• Counters are summed across audio streams
• Non-audio stats are ignored
• Missing peer connection gives zeros
• Flat fields are unchanged (existing tests pass)

🤖 Generated with Claude Code

[bwappsec]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.