feat(xai): add Grok Imagine video generation (/v1/videos) + CLI

Async video job proxy mirroring the existing image-generation layer split:
Next routes → src/sse/handlers/videoGeneration.js (auth gate, account
fallback loop, refresh persistence) → open-sse/handlers/videoCore.js
(transparent upstream proxy, 401 refresh-once/retry-once, secret sanitization).

- POST /v1/videos/{generations,edits,extensions}: byte-exact body forward
  (JSON + multipart), request_id passthrough, Idempotency-Key forwarded
- GET /v1/videos/{request_id}: status/progress/video.url passthrough
- Register grok-imagine-video (kind: "video"); add "video" to MODEL_TYPE_TO_KIND
  so video models stay out of chat lists (also fixes runwayml leak)
- 9router xai video CLI: submit → poll → atomic MP4 download
- No auto-retry of creation POSTs (billable jobs); rotate accounts only on
  401/403/429; sanitize Bearer tokens + credential values from errors/logs

Closes #1285

src/app/api/v1/models/route.js

@@ -94,6 +94,7 @@ const MODEL_TYPE_TO_KIND = {
   embedding: "embedding",
   stt: "stt",
   imageToText: "imageToText",
+  video: "video",
 };
 
 function modelKind(model) {

src/app/api/v1/videos/[id]/route.js

@@ -0,0 +1,17 @@
+import { handleVideoGet } from "@/sse/handlers/videoGeneration.js";
+
+export async function OPTIONS() {
+  return new Response(null, {
+    headers: {
+      "Access-Control-Allow-Origin": "*",
+      "Access-Control-Allow-Methods": "GET, OPTIONS",
+      "Access-Control-Allow-Headers": "*",
+    },
+  });
+}
+
+/** GET /v1/videos/{request_id} - poll async video job status (xAI Grok Imagine) */
+export async function GET(request, { params }) {
+  const { id } = await params;
+  return await handleVideoGet(request, id);
+}

src/app/api/v1/videos/edits/route.js

@@ -0,0 +1,16 @@
+import { handleVideoCreate } from "@/sse/handlers/videoGeneration.js";
+
+export async function OPTIONS() {
+  return new Response(null, {
+    headers: {
+      "Access-Control-Allow-Origin": "*",
+      "Access-Control-Allow-Methods": "POST, OPTIONS",
+      "Access-Control-Allow-Headers": "*",
+    },
+  });
+}
+
+/** POST /v1/videos/edits - async video edit (xAI Grok Imagine) */
+export async function POST(request) {
+  return await handleVideoCreate(request, "edits");
+}

src/app/api/v1/videos/extensions/route.js

@@ -0,0 +1,16 @@
+import { handleVideoCreate } from "@/sse/handlers/videoGeneration.js";
+
+export async function OPTIONS() {
+  return new Response(null, {
+    headers: {
+      "Access-Control-Allow-Origin": "*",
+      "Access-Control-Allow-Methods": "POST, OPTIONS",
+      "Access-Control-Allow-Headers": "*",
+    },
+  });
+}
+
+/** POST /v1/videos/extensions - async video extension (xAI Grok Imagine) */
+export async function POST(request) {
+  return await handleVideoCreate(request, "extensions");
+}

src/app/api/v1/videos/generations/route.js

@@ -0,0 +1,16 @@
+import { handleVideoCreate } from "@/sse/handlers/videoGeneration.js";
+
+export async function OPTIONS() {
+  return new Response(null, {
+    headers: {
+      "Access-Control-Allow-Origin": "*",
+      "Access-Control-Allow-Methods": "POST, OPTIONS",
+      "Access-Control-Allow-Headers": "*",
+    },
+  });
+}
+
+/** POST /v1/videos/generations - async video generation (xAI Grok Imagine) */
+export async function POST(request) {
+  return await handleVideoCreate(request, "generations");
+}