ui: apply interface polish from design article review

- Add global font smoothing (antialiased) to body
- Add tabular-nums to all numeric displays: MetricCard values, Costs page,
  AgentDetail token/cost grids and tables, IssueDetail cost summary,
  Companies page budget display
- Replace markdown image hard border with subtle inset box-shadow overlay
- Replace all animate-ping status dots with calmer animate-pulse across
  AgentDetail, IssueDetail, Agents, sidebar, kanban, issues list, and
  active agents panel

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/index.css

@@ -123,7 +123,7 @@
     -webkit-tap-highlight-color: color-mix(in oklab, var(--foreground) 20%, transparent);
   }
   body {
-    @apply bg-background text-foreground;
+    @apply bg-background text-foreground antialiased;
     height: 100%;
     overflow: hidden;
   }
@@ -528,8 +528,8 @@
 }
 
 .paperclip-markdown img {
-  border: 1px solid var(--border);
   border-radius: calc(var(--radius) + 2px);
+  box-shadow: inset 0 0 0 1px color-mix(in oklab, var(--foreground) 10%, transparent);
 }
 
 .paperclip-markdown table {