Guard shared event bus lifecycle transitions

[vultuk]

Summary

• add an orchestrator event-intake reducer that validates tenant ownership before committing shared event-bus state
• reject stale attempts, stale or duplicate revisions, and invalid lifecycle transitions while preserving the current run state
• emit sanitized audit decisions and event_intake metrics without copying private runtime payloads
• expose the guard from OrchestrationEngine.ingest_event()
• include current-main suite-health fixes for AgentStatus export and metrics timer lock re-entry so the full suite can run cleanly

Validation

• uv run pytest tests/test_event_intake.py tests/test_metrics.py tests/test_scheduler.py -q -> 15 passed
• uv run pytest -q -> 28 passed
• uv run flake8 src/orchestrator/event_intake.py src/orchestrator/engine.py src/orchestrator/__init__.py src/agent/__init__.py src/common/metrics.py tests/test_event_intake.py -> passed
• python3 -m py_compile src/orchestrator/event_intake.py src/orchestrator/engine.py src/orchestrator/__init__.py src/agent/__init__.py src/common/metrics.py tests/test_event_intake.py -> passed
• git diff --check -> passed
• Star gate verified: viewerHasStarred=true

Fixes #1870

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