Fix Workshop attribution for scheduled agent runs

[dcellison]

Summary

• keep scheduled agent prompts as canonical run inputs for context and audit provenance
• exclude those internal human-attributed records from loaded and live Workshop client timelines
• preserve agent-authored scheduled reminders as visible messages
• advance live timeline cursors across hidden scheduler records to prevent replay loops

Validation

• make test — 6,083 passed
• make check
• make typecheck

Installed qualification

The defect was reproduced during the core-scheduler qualification: the scheduled
agent prompt appeared in Workshop as a new message from the owning human
immediately before the agent result. After merge and install, repeat a one-time
scheduled agent run and confirm that only the agent result appears in Workshop.