wip: context-meter + model-label UI and provider/inference tweaks

Checkpoint of in-flight work so the orchestrator branch can rebase onto a
clean main: ContextBar → ContextMeter, model-label helper, model/agent picker
+ provider-snapshot/registry changes, inference payload + message-columns.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/MobileTabSwitcher.tsx

@@ -198,7 +198,7 @@ export function MobileTabSwitcher({
         <button
           type="button"
           onClick={onPillClick}
-          className="flex-1 w-full inline-flex items-center gap-1.5 min-h-[44px] px-3 text-sm rounded-full bg-muted/40 hover:bg-muted/70 text-foreground min-w-0 relative"
+          className="flex-1 w-full inline-flex items-center gap-1.5 min-h-[36px] px-3 text-sm rounded-full bg-muted/40 hover:bg-muted/70 text-foreground min-w-0 relative"
           aria-label="Switch pane"
           style={{
             transform: `translateX(${dragX}px)`,