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/pages/Companies.tsx

@@ -244,7 +244,7 @@ export function Companies() {
                     {issueCount} {issueCount === 1 ? "issue" : "issues"}
                   </span>
                 </div>
-                <div className="flex items-center gap-1.5">
+                <div className="flex items-center gap-1.5 tabular-nums">
                   <DollarSign className="h-3.5 w-3.5" />
                   <span>
                     {formatCents(company.spentMonthlyCents)}