Decouple bundled UI from runtime API and add remote instance tooling (#1228)

Add a packaged-client runtime boundary so the shared UI can talk to local,
desktop, remote, and VS Code runtimes through the right transport instead of
assuming one same-origin web server.

Centralize OpenChamber-owned API access behind RuntimeAPIs, runtimeFetch, and
runtime URL helpers, while keeping official OpenCode traffic on the SDK path.
Support runtime switching, remote host selection, desktop client credentials,
and headless connection links for pairing packaged clients with remote
OpenChamber servers.

Harden the new auth model by moving long-lived client tokens out of browser
URLs, introducing short-lived scoped URL tokens for browser-owned transports,
restricting URL-token access to explicit readable/realtime routes, and making
client-token management session-scoped or self-scoped as appropriate.

Update browser-owned assets and preview proxy flows to work with the split
runtime model, including authenticated project icons, preview token propagation,
CSP-safe preview bridge injection, and preview proxy auth that survives
short-lived URL-token expiry.

Tighten Electron security boundaries for packaged clients by gating privileged
preload state to trusted origins and requiring explicit confirmation before
connect deep-links import or switch remote runtimes.

Also refresh agent guidance and project skills so future runtime/API, auth,
preview, UI, CLI, settings, locale, and drag-to-reorder work follows the new
architecture.

packages/docs/content/docs/ko/environment.mdx

@@ -17,6 +17,10 @@ OpenChamber 웹 서버가 바인딩할 주소입니다. 다른 컴퓨터에서
 
 브라우저 UI 비밀번호입니다. localhost 밖으로 바인딩하거나 터널, 리버스 프록시를 사용할 때 설정하세요.
 
+### `OPENCHAMBER_API_ONLY`
+
+`true` 또는 `1`이면 OpenChamber를 headless 모드로 시작합니다. 데스크톱과 모바일 클라이언트용 API route는 계속 사용할 수 있지만 브라우저 UI는 제공하지 않습니다.
+
 ### `OPENCHAMBER_DATA_DIR`
 
 OpenChamber 데이터 디렉터리를 바꿉니다. 기본값은 `~/.config/openchamber`입니다.