Scheduled tasks overwritten when switching accounts (no namespace isolation)

Description

Scheduled tasks stored at ~/.claude/scheduled-tasks/ are not namespaced by account. When a user switches from one account (e.g., Team) to another (e.g., Max) and creates a scheduled task with the same name, the new task silently overwrites the existing task's SKILL.md file.

Steps to Reproduce

1. On Account A, create a local scheduled task named "morning-brief" with a detailed SKILL.md
2. Switch to Account B (e.g., upgrade from Team to Max)
3. Create a local scheduled task named "morning-brief" on Account B
4. Observe that ~/.claude/scheduled-tasks/morning-brief/SKILL.md has been overwritten with the new placeholder content

Expected Behavior

Tasks should be namespaced per account, e.g.:
~/.claude/scheduled-tasks/{account-id}/morning-brief/

Or at minimum, the Desktop app should warn before overwriting an existing task directory.

Actual Behavior

The SKILL.md is silently overwritten. The original task content is permanently lost with no warning or backup.

Impact

Lost all custom SKILL.md content for two scheduled tasks (morning-brief and morning-brief-daily-archive) during an account migration from Team to Max. No way to recover the content.

Environment

• Claude Code v2.1.86
• macOS (Darwin 24.6.0)
• Claude Desktop app (local scheduled tasks)