Fixes #51733

The previous fix in #32590 only filtered `.vscode` tasks at the modal
presentation layer, so they still appeared in other code paths and in
the used-tasks list. This moves the filtering into
`worktree_scenarios()` in the task inventory, so all consumers see the
correct behavior.

Changes:
- `InventoryFor::worktree_scenarios()` now skips `.vscode` entries when
`.zed` entries exist for the same worktree
- `used_and_current_resolved_tasks()` filters previously spawned
`.vscode` tasks from the used-tasks list
- Removes the now-redundant `.vscode` filter from the task picker modal

Release Notes:

- Fixed .vscode/tasks.json still being used when .zed/tasks.json is
present

Co-authored-by: moktamd <moktamd@users.noreply.github.com>