Document schedule table lifecycle

[clockwork-labs-bot]

Summary

• document schedule row lifecycle differences for scheduled reducers, scheduled procedures, and interval schedules
• clarify that scheduled functions should read row data from the argument they receive
• document the scheduler's in-memory queue behavior when a schedule row is deleted before its queued entry fires

Fixes #5252

Testing

• pnpm build from docs/

Note: docs build completed successfully. It emitted the existing docusaurus-plugin-llms-txt warning for /docs/ask-ai/ask-ai being skipped during HTML-to-Markdown conversion.