v2.1: Bundle Bird X search - no external CLI needed

Vendor Bird's Twitter GraphQL search client directly into /last30days,
eliminating the dependency on `npm install -g @steipete/bird`. X search
now works out of the box with just Node.js 22+ and browser cookies.

- Add vendored bird-search.mjs wrapper (search-only subset of Bird v0.8.0)
- Vendor @steipete/sweet-cookie for browser cookie extraction
- Update bird_x.py to call vendored Node.js module instead of `bird` binary
- Update README.md and SKILL.md for v2.1 (remove Bird CLI install steps)
- Include Bird's MIT LICENSE in vendor directory

The fallback chain is: vendored search -> xAI API key -> web-only mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/lib/vendor/bird-search/lib/paginate-cursor.js

@@ -0,0 +1,37 @@
+export async function paginateCursor(opts) {
+    const { maxPages, pageDelayMs = 1000 } = opts;
+    const seen = new Set();
+    const items = [];
+    let cursor = opts.cursor;
+    let pagesFetched = 0;
+    while (true) {
+        if (pagesFetched > 0 && pageDelayMs > 0) {
+            await opts.sleep(pageDelayMs);
+        }
+        const page = await opts.fetchPage(cursor);
+        if (!page.success) {
+            if (items.length > 0) {
+                return { success: false, error: page.error, items, nextCursor: cursor };
+            }
+            return page;
+        }
+        pagesFetched += 1;
+        for (const item of page.items) {
+            const key = opts.getKey(item);
+            if (seen.has(key)) {
+                continue;
+            }
+            seen.add(key);
+            items.push(item);
+        }
+        const pageCursor = page.cursor;
+        if (!pageCursor || pageCursor === cursor) {
+            return { success: true, items, nextCursor: undefined };
+        }
+        if (maxPages !== undefined && pagesFetched >= maxPages) {
+            return { success: true, items, nextCursor: pageCursor };
+        }
+        cursor = pageCursor;
+    }
+}
+//# sourceMappingURL=paginate-cursor.js.map