feat: move Eligibility Checks into overflow menu in home nav

[morissette]

Closes #289

Summary

Eligibility Checks was presented as a peer tab alongside Screeners in the home screen navbar, giving it equal visual prominence. This moves it into a ... overflow menu on the right side of the navbar so Screeners is clearly the primary navigation item.

Before: Two equal tabs — Screeners | Eligibility checks

After: One primary tab — Screeners — with a ... menu button on the right that reveals Eligibility Checks in a dropdown.

Changes

BdtNavbar.tsx

• Add optional menuDef prop ({ items: { key, label, onClick }[] })
• When provided, renders a ... button (using the existing MenuIcon) right-aligned in the navbar
• Clicking opens a dropdown; clicking outside or selecting an item closes it
• Refactored tabDefs.map() to <For> (Solid.js idiomatic)

HomeScreen.tsx

• Remove checks from tabDefs
• Add menuDef with Eligibility Checks as the single menu item

Test plan

• Home screen loads with only "Screeners" tab visible
• ... button appears on the right side of the navbar
• Clicking ... opens a dropdown with "Eligibility Checks"
• Clicking "Eligibility Checks" switches the view and closes the dropdown
• Clicking outside the menu closes the dropdown
• Navigating back from a screener still shows the correct home view

🤖 Generated with Claude Code

[prestoncabe]

Thanks @morissette - The menu appears to look and function well, but now I think there is an unintended consequence where we lose a visual indicator of which area of the app we're in.

Before this acted as a tab, with an underline:

curious if @Justin-MacIntosh or @Michael-Dratch or @earth-walker have any thoughts on this - My naive thought is that when you navigate to Eligibility Checks, the nav bar would clear except for a bold "Eligibility Checks" title and a "Back to Home" link would be added to the top right. (This would be consistent to the behavior when navigating into a particular screener):

[morissette]

Thinking about these requested changes, should find time to work on them today.