Fix replan publish-only actions and prompt artifact noise

[nathanwhit]

Summary

• omit worker_log artifacts from replan prompt artifact compaction so stdout logs do not consume planner context
• allow worker-bound publish/update PR actions as action-only continue plans after a worker has already completed
• update replan prompt instructions and add regression coverage for both cases

Validation

• go test ./internal/orchestrator -run 'TestReplanDecision|TestCompactArtifactsOmitsWorkerLogs|TestCodexBrainReplanPromptCompactsLargeState'\n- go test ./internal/orchestrator -run TestServiceWaitsForProviderCapacityWhenUsageExhaustedWithoutFallback -count=1\n- go test ./internal/orchestrator