test: deepen and complete project-wide test coverage (#297)

* test: deepen coverage for health doctor provider and tunnels

* test: add broad trait and module re-export coverage

src/onboard/mod.rs

@@ -1,3 +1,17 @@
 pub mod wizard;
 
 pub use wizard::{run_channels_repair_wizard, run_quick_setup, run_wizard};
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn assert_reexport_exists<F>(_value: F) {}
+
+    #[test]
+    fn wizard_functions_are_reexported() {
+        assert_reexport_exists(run_wizard);
+        assert_reexport_exists(run_channels_repair_wizard);
+        assert_reexport_exists(run_quick_setup);
+    }
+}