feat: add bounded HTTP response snapshots to telemetry

[emmepra]

Summary

• persist bounded structured HTTP response snapshots alongside action telemetry previews
• add agent-launcher config knobs and focused tests for snapshot capture
• document telemetry query surfaces and snapshot tuning

Testing

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 pytest -q services/agent-launcher/tests/unit/test_http_snapshot.py services/agent-launcher/tests/integration/test_heartbeat_endpoint_multiround.py -k "telemetry or http_snapshot"
• git diff --check