Proposed changes to search UI

Currently on each dashboard:

• An "all tags" section is visible, i.e. "Tags matching: /.*/"
• Tag sections are collapsed
• Entering a search causes the "all tags" section to drill down
• Clearing the search box causes the "all tags" section to disappear

We've received feedback from multiple individuals that the first thing they do in their workflows is collapse the first section and open the other ones.

It might be better to change the UI to the following:

1. Remove "all tags" section
2. Expand all sections by default (should be possible, thanks to pagination)
3. Make search bar invisible by default (free up vertical whitespace: content is king)
4. Add magnifying glass icon (left to refresh button) that toggles visibility of search bar
5. When initially clicked, search bar initializes to empty (defined as .*) and "all tags" section appears
6. Typing search term causes the "Tags matching" section to update in real time, as it does now
7. Maybe put "x" button to right of search bar that does same thing as clicking search button in top right corner a second time (de-toggling)
8. Ensure that all these search states persist to the fragment section of the URL bar

Thoughts @wchargin @chihuahua @dandelionmane?

Start by locating the dashboard search UI and the code that stores search state in the URL fragment. Compare the current section, search-bar, and toggle behavior with the eight proposed states; done means the revised defaults, live filtering, optional close control, and URL persistence all work consistently.