Metrics from cloud sessions can be sent through the session's own connection

Claude Code can send usage metrics using OpenTelemetry, a standard format for reporting them. In a remote session (one running on a server rather than your computer), it now has another route for them. It is used when all of these hold:

• CLAUDE_CODE_REMOTE is set
• OTEL_EXPORTER_OTLP_METRICS_ENDPOINT exactly matches the session's own metrics address, built from SESSION_INGRESS_URL and CLAUDE_CODE_REMOTE_SESSION_ID and ending in /worker/otlp/metrics
• no OpenTelemetry headers are configured

Metrics then go to that address, signed with CLAUDE_CODE_SESSION_ACCESS_TOKEN. This route is checked before the existing route that uses ANTHROPIC_BASE_URL.