fix(web): modal first-click, card order, cache hint

Three dashboard polish fixes:

- `showModal()` was called straight from the htmx response handler, outside
  the user's own click, so the first click on the dialog's Confirm button was
  swallowed while the top-layer/focus handoff settled. Defer it one animation
  frame and focus Confirm, so a single click confirms.
- Reorder the grid so infrastructure health (Host/VMware/Runners/Cache) reads
  before the VM table instead of after it.
- Drop the Maintenance purge-semantics hint duplicated in the Cargo cache
  card; it already sits next to the buttons it describes.

src/ci_orchestrator/web/static/app.js

@@ -99,7 +99,20 @@
       if (dialog.open) {
         dialog.close();
       }
-      dialog.showModal();
+      // showModal() is called here from an htmx response handler, not
+      // synchronously inside the user's own click -- some browsers then
+      // swallow the very first click on the dialog's contents (the
+      // top-layer promotion/focus handoff hasn't settled), so Confirm
+      // silently does nothing until clicked a second time. One animation
+      // frame is enough for that to settle; explicitly focusing Confirm
+      // afterwards makes the browser's hit-testing land on the button.
+      requestAnimationFrame(function () {
+        dialog.showModal();
+        var confirmBtn = dialog.querySelector('button[type="submit"]');
+        if (confirmBtn) {
+          confirmBtn.focus();
+        }
+      });
     }
     var cancel = dialog.querySelector("[data-modal-cancel]");
     if (cancel) {