feat(web): add dispatchFor transport helper for same-origin proxy

packages/web/src/lib/dispatch.ts

@@ -0,0 +1,36 @@
+import { httpFetch } from "@/lib/http";
+import { isTauri } from "@/lib/platform";
+
+/** Same-origin path prefix the web build issues all Honcho calls through. */
+export const API_PREFIX = "/api";
+/** Request header naming the real Honcho upstream for the proxy to forward to. */
+export const UPSTREAM_HEADER = "X-Honcho-Upstream";
+/** Response header the proxy sets on its OWN refusals (so they aren't read as upstream auth). */
+export const PROXY_REJECT_HEADER = "X-Honcho-Proxy-Reject";
+
+export interface Dispatch {
+	baseUrl: string;
+	headers: Record<string, string>;
+	fetch: typeof globalThis.fetch;
+}
+
+function normalizeUpstream(url: string): string {
+	return url.trim().replace(/\/+$/, "");
+}
+
+/**
+ * Resolve how to issue a request for an instance.
+ * - Web: same-origin `/api` + `X-Honcho-Upstream` header (proxy forwards server-side, no CORS).
+ * - Tauri: the absolute instance URL via reqwest (no browser same-origin policy).
+ */
+export function dispatchFor(instance: { baseUrl: string; token?: string }): Dispatch {
+	const headers: Record<string, string> = { "Content-Type": "application/json" };
+	if (instance.token) headers.Authorization = `Bearer ${instance.token}`;
+
+	if (isTauri()) {
+		return { baseUrl: instance.baseUrl, headers, fetch: httpFetch };
+	}
+
+	headers[UPSTREAM_HEADER] = normalizeUpstream(instance.baseUrl);
+	return { baseUrl: API_PREFIX, headers, fetch: httpFetch };
+}