Document creating, supervising, and stopping a recurring task from mecatui #2391

Reader need

"Run this useful task regularly, show me what happened, and let me pause or stop it."

Current gap

user-docs/features/sessions/scheduled-tasks.md mentions the in-chat Schedule tool and /schedule, but its worked creation example moves quickly into REST. Terminal users need a complete client workflow.

Proposed work

Document one realistic read-only recurring task, such as a repository activity summary, using a normal prompt and the /schedule interface. Follow creation through inspection, a run/result, and pausing or deleting the schedule. Keep scheduler storage, authority, placement, delivery, and API contracts in their current canonical owners.

Acceptance criteria

• Include a copyable prompt with a clear task, recurrence, time zone, expected output, and read-only intent.
• Explain required connected-server availability and how to verify what was scheduled.
• Show how to inspect status and results, handle a failed/missed run at the user-workflow level, and pause/delete future executions.
• Distinguish pausing/deleting future runs from cancelling an already active run, according to implemented behavior.
• Verify result-delivery claims against shipped behavior and consider open completion-reporting issue Fix scheduled-task completion reporting in the initiating chat #700; do not promise unimplemented notifications or recurrence controls.
• Link the recipe from Use Mecatl and retain the canonical Scheduled tasks page for shared semantics.

Tracking

Part of #2386. Follow the parent issue's shared ownership and validation criteria.