fix: publish unavailable watcher snapshots safely

[Pigbibi]

Summary

• treat accepted P1 terminal records with no comparable P3 observations as an unavailable source state, not a workflow error
• always publish the bounded, no-order research-task source snapshot on successful scheduled watcher runs
• preserve deferred P1 records as issue-only findings and add regression coverage

Safety

• no strategy changes, broker calls, deployments, or live authority
• unavailable snapshots contain no tasks and remain explicitly marked unavailable

Verification

• pytest -q tests/test_run_strategy_optimization_watcher.py tests/test_strategy_optimization_watcher_workflow.py