chore(ci): restore nucleus downstream testing (#5497)

* chore(ci): restore nucleus config

we don't need it for releases, but still need it for downstream testing

* chore(ci): disable nucleus releases

hopefully

Author: wjhsf

.nucleus.yaml

@@ -0,0 +1,64 @@
+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:
+                - BuilderFramework/builder-framework-salesforce
+                - MobilePlatform/lsdk-modules
+                - MobilePlatform/lwr-lightning-platform
+                - MobilePlatform/ui-fsm-components
+                - automation-platform/ui-externalservices-builder-components
+                - communities/microsite-template-marketing
+                - communities/shared-experience-components
+                - communities/ui-commerce-components
+                - communities/webruntime
+                - lds/lds-plugins
+                - salesforce-experience-platform-emu/komaci
+                - salesforce-experience-platform-emu/locker-pentest-app
+                - salesforce-experience-platform-emu/lwr
+                - salesforce-experience-platform-emu/lwr-everywhere
+                - salesforce-experience-platform-emu/lwr-recipes
+                - salesforce/lwc-test
+                # Using old major versions; tests in PRs will always fail
+                # - salesforce/o11y-sample-app
+                # - Skilling-and-Enablement/ui-external-enablement
+    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