feat(dashboard): GuruConnect v2 operator console (pass 1)

React + Vite + TypeScript SPA: scaffold, operations-terminal design
system, Bearer-token auth, and the Machines view.

- Design system: OKLCH-tinted dark theme (ink-slate + signal-cyan),
  Hanken Grotesk + JetBrains Mono, status-color language
  (online/offline/granted/pending/denied/not_required), motion with
  prefers-reduced-motion honored.
- Auth: token in sessionStorage via ref (never React state), protected
  routes, 401 session teardown, admin-gated per-agent-key UI.
- Machines view: data table (sticky header, keyboard-activated rows,
  skeleton loading, actionable empty/error states), non-blocking detail
  drawer, delete confirm, admin key management with copy-once reveal.
- UI primitives: Modal (focus trap + inert + portal + dialogStack),
  Drawer, Table, Badge/StatusDot, toast, states.
- Typed API client normalizing the two error-envelope shapes.

Passed Code Review (no blockers), impeccable critique-and-polish, and
local gates (tsc/lint/build green). Dev-only Vite proxy to :3002.

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

dashboard/src/components/ui/dialogStack.ts

@@ -0,0 +1,28 @@
+// A tiny module-level stack so only the topmost open dialog (Modal or Drawer)
+// reacts to Escape and owns the background `inert` toggle. This keeps stacked
+// dialogs (e.g. a confirm on top of a management modal) from all closing at once.
+
+const stack: symbol[] = [];
+
+/** Push a dialog onto the stack. Returns its token. */
+export function pushDialog(): symbol {
+  const token = Symbol("dialog");
+  stack.push(token);
+  return token;
+}
+
+/** Remove a dialog from the stack by token. */
+export function popDialog(token: symbol): void {
+  const i = stack.lastIndexOf(token);
+  if (i !== -1) stack.splice(i, 1);
+}
+
+/** True when `token` is the topmost open dialog. */
+export function isTopDialog(token: symbol): boolean {
+  return stack.length > 0 && stack[stack.length - 1] === token;
+}
+
+/** True when any dialog is open. */
+export function hasOpenDialog(): boolean {
+  return stack.length > 0;
+}