[agentydragon]

Summary

Replace the test-only Client.events SSE parser with typed ReadSessionEvents pages through the existing authenticated App History facade. A shared reader validates cursor coverage, applies settlement/removal corrections, and retries only idempotent History reads during App outages.

Migrate the system-test Agent, setup, native-artifact, storage, and suspend/resume consumers while preserving command-admission, completed-turn/setup, correction, and raw archive-watermark behavior. Record this first slice in the task DAG.

The direct HTTP SSE tests and consumers, App SSE route, and route-specific bridge remain for the separately scoped retirement slice. Native History clients remain gRPC; this adds no reader grant or browser-credential forwarding.

Validation

• direnv exec . bbr test //agentplane/app/testing:test_client //agentplane/system_tests/driver:test_agent
• direnv exec . bbr build //agentplane/app/testing:client //agentplane/app/testing:history_reads //agentplane/app/testing:test_client //agentplane/system_tests/driver:agent //agentplane/system_tests/driver:native_artifacts //agentplane/system_tests/driver:session_setup //agentplane/system_tests/driver:test_agent //agentplane/system_tests/scenarios:storage //agentplane/system_tests/scenarios:suspend_resume
• direnv exec . bb run //devinfra:gazelle
• direnv exec . pre-commit run --files for all changed files