Phase 7: polish — overview health, reduced-motion, mobile, a11y, copy-ids

- Overview health hero derives from subsystem probes when the backend gives no
  overall status, so it never says "Unknown" next to an all-Healthy Subsystems
  card (the audit's most jarring contradiction). Home error copy now uses the
  Phase-2 describeError instead of raw backend strings.
- Global prefers-reduced-motion guard (transitions, loops, aurora field) +
  motion-reduce on the sidebar width transition.
- Mobile: content reserves a top row (pt-16 md:p-6) so the floating hamburger
  never overlaps the page H1.
- A11y: collapsed rail items get an explicit aria-label.
- Monitoring: disk "busiest mount" tile shows the % as the value and the long
  mount path as a truncated caption, so it no longer clips mid-word.
- New CopyId component (click-to-copy UUIDs), wired into Profile.

Typecheck 36→36, 24-route sweep clean. Remaining items (lib a11y labels,
table aria-sort, dev-only monitoring data) noted in the spec.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/app.css

@@ -156,3 +156,21 @@
   }
 }
 
+
+/* Accessibility: honour a reduced-motion request. Skyrise leans on ambient
+ * drift (the aurora field), spring transitions, and looping keyframes; for
+ * anyone who asks for less motion, near-instant everything and freeze the
+ * decorative loops. This is the global guard the app previously lacked. */
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.01ms !important;
+    animation-iteration-count: 1 !important;
+    transition-duration: 0.01ms !important;
+    scroll-behavior: auto !important;
+  }
+  [data-slot="aurora-field"] {
+    animation: none !important;
+  }
+}