fix(cart): add WebSocket heartbeat pings, exponential reconnect, and eliminate 5s GET polling

[HimanM]

Summary of Changes

1. 💓 WebSocket Heartbeat Pings (25s Interval)

• Periodically sends {"type": "ping"}\ across the cart WebSocket to keep the TCP connection alive through Nginx, Cloudflare, Vercel, and cloud proxies.
• Prevents cloud firewalls and reverse proxies from dropping idle sockets after 30–60 seconds of inactivity.

2. 🔄 Smart Exponential Auto-Reconnect

• Replaces the legacy fallback with an exponential backoff reconnect loop (1.5s, 3s, 6s, max 10s).
• Automatically queries and updates cart state on reconnection to guarantee 100% data consistency.

3. 👁️ Tab Focus Revalidation

• Automatically checks WebSocket connectivity and re-verifies cart state when the user focuses back into the browser tab.

4. 🚫 Eliminated 5-Second HTTP GET Polling Spam

• Removed the continuous \setInterval(fetchCart, 5000)\ polling loop that caused recurring \GET /api/cart/sess-...\ requests in production network tabs.

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Validation

• 
  pm run test:cart-revision: Passed (100%)
• 
  pm run test:recent-carts: Passed (100%)
• 
  pm run test:session-store: Passed (100%)
• 
  px next build: Compiled with 0 errors

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Project	Deployment	Actions	Updated (UTC)
kapruka-mcp-agent	Ready	Preview	Aug 17, 2026 10:13am