Search: Switch to All Notes

### Description:
When a Search Session begins, we should switch to **All Notes**, for consistency reasons (since we're not filtering by tag anymore).

Thank you @pachlava for suggesting this one!

Start at the entry point where a Search Session begins and trace how the current note filter is selected. Change the session to use All Notes rather than a tag-filtered view, then verify that beginning a search consistently shows all notes.

Written by the indexing model from the issue text.