Replace per-port cloudflared tunnels with /proxy/:port reverse proxy

Route all localhost previews through the existing Express reverse proxy
instead of spawning separate cloudflared quick tunnels per port. This
avoids Cloudflare rate-limiting on ephemeral DNS registrations.

- BrowserPage: vertical session list with proxy reachability checks,
  copy/go/delete per row, inline add-port input
- browserStore: remove socket-based tunnel cleanup
- socket-handlers: remove all tunnel socket handlers
- tunnel.ts: delete per-port tunnel functions, simplify stopAllTunnels
- InputBox: code tab vendor selector as portal dropup with triangle toggle
- README: document proxy architecture and dev server notes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: davindicode

README.md

@@ -76,8 +76,8 @@
 
 ### Layout & Access
 - **Responsive** — 3-column resizable panels on desktop/landscape, single-panel with bottom tab bar on mobile/portrait (orientation-aware breakpoint)
-- **Localhost Browser** — reverse proxy to preview any localhost port, multi-tab with console output
-- **Cloudflare Tunnel** — one command (`./start.sh`) to build, start, and expose via public URL
+- **Localhost Browser** — preview any localhost port via `/proxy/:port` reverse proxy (single tunnel, no per-port cloudflared processes), multi-tab with reachability checks
+- **Cloudflare Tunnel** — one command (`./start.sh`) to build, start, and expose via public URL; all localhost previews route through the same tunnel
 
 ## Quick Start
 
@@ -146,12 +146,24 @@ Express (port 7777)
 ├── React Router v7 — UI (SSR shell + client-side app)
 ├── Socket.IO — real-time terminal I/O via node-pty
 ├── REST API — file operations (list, read, write, rename, delete, upload, download, mkdir)
-├── Reverse Proxy — /proxy/:port/* forwards to localhost services
-└── Cloudflare Tunnel — optional public URL via cloudflared
+├── Reverse Proxy — /proxy/:port/* forwards HTTP + WebSocket to localhost services
+└── Cloudflare Tunnel — single optional tunnel via cloudflared (all traffic, including localhost previews)
 ```
 
 All three panels (Files, Terminal, Browser) are always mounted in the DOM with CSS visibility toggling — preserving terminal state, WebSocket connections, and iframe content across navigation.
 
+### Localhost Preview
+
+The Browser tab previews any localhost port through the Express reverse proxy — no extra tunnels or processes are spawned. When you enter a port, the UI checks reachability via `/proxy/:port/` and gives you a link to open in a new tab.
+
+The proxy handles:
+- **Path rewriting** — strips the `/proxy/:port` prefix before forwarding to `127.0.0.1:<port>`
+- **WebSocket upgrades** — WS connections on `/proxy/:port/...` are forwarded (supports Vite HMR, webpack-dev-server, etc.)
+- **Header stripping** — removes `X-Frame-Options` and CSP headers so content can embed
+- **Asset path rewriting** — rewrites absolute paths in HTML, CSS, JS (src, href, url(), ES imports) to include the `/proxy/:port` prefix
+
+**Dev server notes:** Most dev servers (Vite, webpack, Next.js) work out of the box since both HTTP and WebSocket traffic are proxied. However, dev servers that hardcode their WebSocket URL to `ws://localhost:<port>` in client-side code (bypassing the proxy path) will fail over the tunnel — the HMR connection won't reach the VPS. Vite works because its HMR client connects relative to the page origin. If a dev server's HMR breaks, configure it to use a relative or custom WebSocket path.
+
 ## Tech Stack
 
 React Router v7, Express, Socket.IO, node-pty, xterm.js, Monaco Editor, Zustand, Tailwind CSS v4, TypeScript