feat: bump buck2-toolchain to v3

Author: sigma

packages/buck2-toolchain/data.json

@@ -1,5 +1,9 @@
 {
-  "_meta": { "default": "2" },
+  "_meta": { "default": "3" },
+  "3": {
+    "buck2": "2026-04-15",
+    "reindeer": "2026.04.27.00"
+  },
   "1": {
     "buck2": "2025-12-01",
     "reindeer": "2026.03.09.00"