(schedules): a Schedules sidebar tab to list, run, enable, create and follow scheduled tasks #792

Problem

Scheduled tasks have no management surface. A schedule only appears as a schedule-*.md file in the Agent Files sidebar tab, with a ▶ Run now button (public/memory-workfiles-view.js:149). Its runs are listed in the Sessions tab under the schedule's header (#489). Creating one goes through the /create-switchboard-schedule command (schedule-ipc.js, SCHEDULE_CREATOR_TEMPLATE). Nothing shows, across projects, which schedules exist, when they next run, whether they are enabled, or how their last run ended.

Decisions (maintainer, 2026-10-26)

1. A dedicated sidebar tab, "Schedules", next to Agent Files. It lists the schedules of every registered schedule project (scheduleRegistry, schedule-runner.js), grouped by project.
2. First version covers all of:
   • List and state: name, project, cron in plain words, next run, last run and its outcome, enabled or not, catch-up.
   • Actions: Run now, enable/disable (setScheduleEnabled), open the file in the editor, delete with confirmation.
   • Creation: a form (name, cron, prompt, allowed tools, and the other frontmatter the runner reads) that writes the schedule-*.md file. It is in addition to /create-switchboard-schedule, which stays.
   • Run history: each schedule's past runs, opening their transcript.
3. schedule-*.md files leave Agent Files. The Schedules tab is the only place they are listed and acted on. Messages that point to Agent Files for schedules (public/sidebar.js:1485, :1488) point to the Schedules tab instead.

To settle in the spec

• Where "last run and its outcome" and "run history" come from (catch-up records under schedule-state, pre-seeded transcripts from createScheduleSession, the main log); what is shown when no record exists.
• Next-run computation from the existing cron parser (cronMatches) and how catch-up and disabled state change it; time zone.
• Validation and write path of the creation form: same frontmatter parser as the runner, refusal of the binds refusedScheduleBinds refuses, atomic write, refusal for a sandboxed or archived project, a name collision.
• Deletion vs disabling, and the scheduleFileUnlinked contract.
• Refresh when a schedule file changes on disk.
• Interaction with (schedules): run a scheduled task as a background session so it can be joined while it runs #611 (run as a background session), (schedules): Run now reports a run that fails after its shell started #707 (Run now reports a run that fails after its shell started).

Spec only for now: no implementation is scheduled.