feat(scheduler): add Windows Task Scheduler support

[shaoohh]

Closes #69.

Summary

• add schtasks as the scheduler provider on Windows
• install and remove the scheduled task by invoking the current runtime and CLI entry directly, avoiding shim-related issues
• add Windows-specific command quoting and idempotent task removal handling
• normalize legacy Windows manual scheduler configs to schtasks
• normalize repo-relative path separators for Windows compatibility in workspace and memory state
• add windows-latest CI coverage for Task Scheduler behavior and document the Windows scheduler flow

Notes

• Windows automation is configured in interactive-only mode (/IT), so the task runs when the user is logged in

Testing

• bun run typecheck
• bun test