fix: add missing react-reconciler peer dependency for checkout-datetime

@shopify/ui-extensions-react's internal @remote-ui/react dependency
requires react-reconciler as a peer dependency, which npm doesn't
auto-install — esbuild failed bundling checkout-datetime with "Could not
resolve react-reconciler" since nothing in the workspace declared it.
Added explicitly to checkout-datetime's package.json at a version
satisfying @remote-ui/react's peer range (>=0.26.0 <0.30.0); npm
workspaces hoists it to the shared root node_modules automatically,
which is where @remote-ui/react's own import resolution needs it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

extensions/checkout-datetime/package.json

@@ -9,7 +9,8 @@
   "dependencies": {
     "@shopify/ui-extensions": "^2025.7.3",
     "@shopify/ui-extensions-react": "^2025.7.3",
-    "react": "^18.3.1"
+    "react": "^18.3.1",
+    "react-reconciler": "^0.29.2"
   },
   "devDependencies": {
     "typescript": "^5.6.3"

package-lock.json

@@ -60,7 +60,8 @@
       "dependencies": {
         "@shopify/ui-extensions": "^2025.7.3",
         "@shopify/ui-extensions-react": "^2025.7.3",
-        "react": "^18.3.1"
+        "react": "^18.3.1",
+        "react-reconciler": "^0.29.2"
       },
       "devDependencies": {
         "typescript": "^5.6.3"
@@ -16603,6 +16604,22 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/react-reconciler": {
+      "version": "0.29.2",
+      "resolved": "https://registry.npmjs.org/react-reconciler/-/react-reconciler-0.29.2.tgz",
+      "integrity": "sha512-zZQqIiYgDCTP/f1N/mAR10nJGrPD2ZR+jDSEsKWJHYC7Cm2wodlwbR3upZRdC3cjIjSlTLNVyO7Iu0Yy7t2AYg==",
+      "license": "MIT",
+      "dependencies": {
+        "loose-envify": "^1.1.0",
+        "scheduler": "^0.23.2"
+      },
+      "engines": {
+        "node": ">=0.10.0"
+      },
+      "peerDependencies": {
+        "react": "^18.3.1"
+      }
+    },
     "node_modules/react-refresh": {
       "version": "0.14.2",
       "resolved": "https://registry.npmjs.org/react-refresh/-/react-refresh-0.14.2.tgz",