Implement /schedule with clear separation between remote triggers and local cron

[yaohaowei0914]

Background

The user-visible /schedule command maps to scheduled remote agents in the Bun reference, but the same codebase also has a separate local cron scheduler. Rust should not blur the two.

Reference

• Remote entry: src/skills/bundled/scheduleRemoteAgents.ts
• Local scheduler base: CronCreateTool/CronListTool/CronDeleteTool, plus src/utils/cronTasks.ts and src/utils/cronScheduler.ts
• Behavior: remote /schedule manages cloud triggers; local cron manages .claude/scheduled_tasks.json and host-side polling.

Rust Gap

• No /schedule today.
• No public local-cron command family either.
• Suggested approach: define the first milestone clearly (remote triggers vs local cron) and keep the two capability lines separate.

Acceptance

• Decide and document the scope of the first /schedule milestone.
• If local cron comes first, include persistence, locking, polling, and task inspection.
• If remote triggers come first, include the needed OAuth/environment/API groundwork.
• Keep user docs explicit about the distinction.