Summary

Add a new cost-tracker extension that provides per-agent cost tracking from telemetry JSONL.

Problem

15 discovery agents running 3 waves/day with zero per-agent cost/spend visibility.

Solution

• New extension extensions/cost-tracker/ that reads from telemetry JSONL sink (additive, no upstream changes)
• Model pricing table covering MiniMax M2.5, GLM-5, Grok 4, Claude Sonnet, Claude Haiku at minimum
• Per-agent daily cost rollup - aggregates token usage × model pricing per agent
• Budget alerts - logs warnings when daily/agent limits exceeded

Deliverables

1. ✅ extensions/cost-tracker/ extension scaffold (package.json, index.ts, cost-aggregator.ts)
2. ✅ Model pricing table (MiniMax M2.5, GLM-5, Grok 4, Claude Sonnet, Claude Haiku)
3. ✅ Per-agent daily cost rollup function reading from telemetry JSONL
4. ✅ Budget alert hook (logs warning when threshold exceeded)
5. ✅ scripts/cost-report.ts — CLI script to print last 24h cost summary
6. ✅ PR to feat/cost-tracker-2

Testing

# Test CLI script
npx tsx scripts/cost-report.ts --telemetryPath /path/to/telemetry

# With custom window
npx tsx scripts/cost-report.ts --telemetryPath /path/to/telemetry --hours 48 --json

Notes

• TypeScript strict, ESM, no any types
• ~200 LOC for core extension logic
• Reads from existing telemetry JSONL format (same as cron_usage_report.ts)
• Zero impact to existing extensions/services