Unchecked task list

### What

A smart list feature that allows users to see all task items that are unchecked in a single location.
### Why

Grants a user a single location to got and view all unchecked off tasks without having to search through all their notes to find any outstanding tasks.
### How

See this [GitHub](https://github.com/delashum/obsidian-checklist-plugin) page for examples on how Obsidian plugin does it.

The issue does not name any files or tests; begin by locating the task-list and note-search entry points in the Simplenote desktop app, using the linked Obsidian checklist plugin as a behavioral reference. Done should provide one location showing all unchecked task items across notes, with the expected behavior and scope agreed before implementation.

Written by the indexing model from the issue text.