[FEATURE]: OpenCode Remote Control

Feature hasn't been suggested before.

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Describe the enhancement you want to request

In corporate environments, developers run OpenCode on dev machines but may need to access it from a browser on a different workstation, behind corporate SSO.

opencode serve already exposes the full API over HTTP, and the web UI embedding API (AppInterface, PlatformProvider, ServerConnection) is well-designed for third-party consumers. These two together make remote access feasible today.

Similar to how Claude Code Remote Control lets users continue local sessions from any browser or mobile device, OpenCode could support a similar workflow — but routed through a self-hosted gateway with corporate OIDC auth.

What's missing is the glue:

• A way to discover and route to multiple dev machines from a single URL
• Corporate OIDC authentication in the browser flow
• A web entry point that wraps the OpenCode UI with user context

How it would work:

1. Developer runs opencode remote-control on their dev machine — it authenticates via OIDC, starts opencode serve, and registers itself with a central gateway
2. Developer opens the gateway's web UI from any browser — authenticates via OIDC, sees their live sessions listed
3. Clicking a session loads the full OpenCode web UI (embedded via AppInterface), proxied through the gateway to the dev machine

Related: #45346 (remote server sessions as tabs) — the gateway would solve the discovery and routing layer that issue assumes is already in place.

I've been building a prototype and have it working end-to-end. The web entry point follows the same embedding pattern as packages/desktop. Would love to discuss whether this is something the project would want to support — open to a PR or a different approach.