## Summary

- Show a confirmation dialog when inline WO number editing detects a duplicate instead of navigating immediately to the existing work order.
- Dialog title: **Duplicate Work Order Number**; actions: **View existing** (opens the existing WO slide-over) and **Dismiss** (closes the dialog and keeps the current row editable).
- Duplicate scan logic in `editable-wo-number-cell.tsx` is unchanged; only the post-detection UX is updated.

## Test plan

- [ ] Edit a WO number in the table to match an existing row → dialog opens with the duplicate number in the message.
- [ ] Click **Dismiss** → dialog closes; edited row keeps its original number.
- [ ] Repeat duplicate entry → click **View existing** → navigates to `/workorders/{id}` for the existing row.
- [ ] Confirm non-duplicate WO number edits still save normally.

## Out of scope

- Server-side uniqueness (422) handling
- SH provisional numbering