feat(FN-3746): document plugin API coverage and add focus-visible states

Completes Step 6 of FN-3746 by adding `focus-visible` states to ProjectCard and ProjectOverview CSS components, and documenting the Even Realities plugin API coverage in the project docs.

Fusion-Task-Id: FN-3746

packages/dashboard/app/components/ProjectOverview.css

@@ -175,6 +175,12 @@
   box-shadow: var(--shadow-sm);
 }
 
+.project-filter-tab:focus-visible {
+  outline: none;
+  border-color: var(--todo);
+  box-shadow: var(--focus-ring-strong);
+}
+
 .project-filter-tab.has-errors {
   color: var(--color-error);
 }