fix: bound Open Design HTTP and SSE transport (#8)

Merge reviewed bounded Open Design HTTP and SSE transport fix for issue #8.

Author: jcarlosrodicio

docs/open-design.md

@@ -23,3 +23,11 @@ Do not use project or file URLs.
 ## Security
 
 Do not expose Open Design directly to the Internet without authentication, VPN, Tailscale, WireGuard, or a secure reverse proxy.
+
+## Runtime budgets
+
+The Open Design client uses fixed safety budgets for remote calls: 5 seconds to
+receive response headers, 15 seconds of read-idle time, 120 seconds total per
+request, 1 MiB for JSON responses, 8 MiB for SSE responses, 2 MiB per stdout or
+stderr channel, and 10,000 SSE events. Oversized, stalled, or incomplete
+responses fail with a bounded diagnostic instead of being retained indefinitely.

opencode/tools/open-design-http.d.mts

@@ -0,0 +1,45 @@
+export type OpenDesignHttpOptions = {
+  fetchImpl?: typeof fetch
+  connectTimeoutMs?: number
+  totalTimeoutMs?: number
+  idleTimeoutMs?: number
+  maxJsonBytes?: number
+  maxSseBytes?: number
+  maxOutputBytes?: number
+  maxEvents?: number
+  maxDiagnosticBytes?: number
+}
+
+export const OPEN_DESIGN_HTTP_LIMITS: Readonly<{
+  connectTimeoutMs: number
+  totalTimeoutMs: number
+  idleTimeoutMs: number
+  maxJsonBytes: number
+  maxSseBytes: number
+  maxOutputBytes: number
+  maxEvents: number
+  maxDiagnosticBytes: number
+}>
+
+export function requestJson(
+  base: string,
+  path: string,
+  init?: RequestInit,
+  options?: OpenDesignHttpOptions,
+): Promise<unknown>
+
+export function parseSseFrames(buffer: string): {
+  frames: Array<{ event: string; data: unknown }>
+  rest: string
+}
+
+export function streamOpenDesignChat(
+  base: string,
+  body: unknown,
+  options?: OpenDesignHttpOptions,
+): Promise<{
+  stdout: string
+  stderr: string
+  end: unknown
+  eventsCount: number
+}>