Built-in create-shortcut skill references non-existent set_scheduled_task tool

## Summary

The built-in `create-shortcut` skill in Cowork references a `set_scheduled_task` tool that does not exist in the session's available tool set. This causes Cowork to get stuck when attempting to create scheduled shortcuts.

## Steps to Reproduce

1. Start a Cowork session
2. Ask Cowork to create a recurring shortcut/scheduled task (e.g., "create a daily morning briefing shortcut")
3. Cowork loads the `create-shortcut` skill
4. The skill instructs Claude to "call the `set_scheduled_task` tool" (line 36 of SKILL.md)
5. Claude cannot find the tool and enters a loop searching for it

## Expected Behavior

The `set_scheduled_task` tool should be available in the session when the `create-shortcut` skill is loaded, OR the skill should not reference a tool that doesn't exist.

## Actual Behavior

Claude's thinking shows it recognizing the problem in real-time:

> "The skill says to call set_scheduled_task — this must be a tool available through the skill. Wait, let me re-read the skill instructions. It says 'call the set_scheduled_task tool.' I don't see this explicitly in my tool list."

The session gets stuck and cannot complete the shortcut creation.

## Skill File Location

```
~/Library/Application Support/Claude/local-agent-mode-sessions//.claude/skills/create-shortcut/SKILL.md
```

## Relevant Skill Content (line 36)

```markdown
Finally, call the "set_scheduled_task" tool.
```

## Environment

- macOS (Darwin 25.1.0)
- Claude Desktop app with Cowork (research preview)
- Max plan
- Date: 2026-02-05