feat: analysis pipeline with staged SSE

Adds @openuidev/lang-core (one-line reason: the prompt-side library must build in a non-React Node runtime; react-lang's createContext crashes the route's server bundle).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/stream.ts

@@ -0,0 +1,36 @@
+export const sse = (event: string, data: unknown) => `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
+
+export async function* readSse(body: ReadableStream<Uint8Array>): AsyncGenerator<{ event: string; data: any }> {
+  const reader = body.getReader(); const dec = new TextDecoder(); let buf = "";
+  while (true) {
+    const { value, done } = await reader.read();
+    if (done) break;
+    buf += dec.decode(value, { stream: true });
+    let at: number;
+    while ((at = buf.indexOf("\n\n")) !== -1) {
+      const frame = buf.slice(0, at); buf = buf.slice(at + 2);
+      const event = /^event: (.+)$/m.exec(frame)?.[1] ?? "message";
+      const raw = /^data: (.*)$/m.exec(frame)?.[1] ?? "";
+      try { yield { event, data: JSON.parse(raw) }; } catch { /* keep-alive or unparsable frame */ }
+    }
+  }
+}
+
+export async function* openAiTextDeltas(res: Response): AsyncGenerator<string> {
+  const reader = res.body!.getReader(); const dec = new TextDecoder(); let buf = "";
+  while (true) {
+    const { value, done } = await reader.read();
+    if (done) break;
+    buf += dec.decode(value, { stream: true });
+    let at: number;
+    while ((at = buf.indexOf("\n\n")) !== -1) {
+      const line = (buf.slice(0, at).split("\n").find((l) => l.startsWith("data:")) ?? "").slice(5).trim();
+      buf = buf.slice(at + 2);
+      if (!line) continue;
+      if (line === "[DONE]") return;
+      let delta: unknown;
+      try { delta = JSON.parse(line)?.choices?.[0]?.delta?.content; } catch { continue; }
+      if (typeof delta === "string" && delta) yield delta;
+    }
+  }
+}