feat: implement tool-session progress panel and live list updates

- Add SessionOperationsContext + SessionProgressPanel for global,
  non-blocking lifecycle progress (create/start/stop/restart/delete/
  recreate-tunnel) driven by SSE events.
- Promote SessionsContext to authoritative shared session state with
  refresh, addOrUpdateSession, and removeSession helpers.
- Wire AppShell, DashboardPage, SessionsPage, useInstanceActions,
  ToolStarter, and InstanceList into shared state so lists update
  immediately after create/delete without manual refresh.
- Remove legacy blocking overlays from CreateSessionForm, SessionCard,
  and InstanceList; keep disabled states and inline spinners only.
- Update DashboardPage tests to wrap with SessionsProvider and
  SessionOperationsProvider.
- Add .cache/ to .gitignore.

Quality gates: npm run typecheck, npm run lint, npm test -- --run
(82 passed).

apps/web/src/components/features/session/session-card.tsx

@@ -105,12 +105,7 @@ export function SessionCard({
 	};
 
 	return (
-		<article className={`card session-card ${isBusy ? "busy" : ""}`}>
-			{isBusy && (
-				<div className="session-busy-overlay">
-					<Icon name="loading" size="md" />
-				</div>
-			)}
+		<article className="card session-card">
 			<div className="session-card-content">
 				<div className="session-card-header">
 					<div className="session-card-title">