Project Parent Task Filter

This module extends the search panel used on the Tasks screen of the Project app (project.task). It does not add new menus or screens; it adds two new options inside the existing Filters and Group By menus.

• A filter named "Parent tasks" that shows only tasks that have no parent task, i.e. the top-level tasks of a project. Tasks that are subtasks of another task are hidden when this filter is active.
• A grouping option also named "Parent tasks" that groups the task list by the parent task, so all subtasks appear together under the task they belong to.

Both options are placed right after the existing "Unassigned" filter in the search form, so they are easy to find alongside the other standard task filters.

The module only changes the search view of tasks; it adds no new fields, no automatic computations, no checks or restrictions, and no emails or scheduled actions. It relies entirely on the existing parent task relationship already provided by the Project app. The README mentions extra behaviour such as showing the number of subtasks in the kanban view and enabling subtasks in project settings, but the code provided only contains the search view change, so only the filter and grouping are described here.