revert(nucleus): add config back (#5676)

but remove all required downstreams

Author: wjhsf

.nucleus.yaml

@@ -0,0 +1,46 @@
+core-deploy:
+    enabled: true
+    project-modules:
+        lwc: lwc.version
+branches:
+    ~DEFAULT~:
+        pull-request: &branch-definition
+            workflow: build-and-test
+            auto-start: true
+            auto-start-from-forks: false
+            merge-method: disabled # do not auto-merge; we'll do it ourselves
+            required-downstream-deps:
+                # none
+    release:
+        pull-request:
+            <<: *branch-definition
+    # Only active branches need to be included in this config
+    winter26:
+        pull-request:
+            <<: *branch-definition
+    spring25:
+        pull-request:
+            <<: *branch-definition
+    summer25:
+        pull-request:
+            <<: *branch-definition
+jobs:
+    build-and-test:
+        memory-limit: 16
+    create-canary-release:
+        memory-limit: 16
+    build-dependency:
+        memory-limit: 16
+    release:
+        memory-limit: 16
+steps:
+    node-conformance:
+        run:
+            command: yarn run lint
+        after: node-build
+    node-unit-tests:
+        run:
+            command: yarn test
+    # this project runs yarn build after yarn install so skip explicit build step
+    node-build: &node-build
+        skip: true