trial: shadow-gen diff (compare_sdk) for the gen-sdk migration

THROWAWAY, DO NOT MERGE. Pre-merge trial of the centralized compare_sdk
reusable workflow (pulumi/ci-mgmt#2300) to survey legacy-vs-gen-sdk gaps.

- adds a temporary compare_sdk Makefile target (refs pinned to the ci-mgmt PR stack)
- adds a standalone compare-sdk-trial workflow (prerequisites + compare_sdk only)
- removes run-acceptance-tests.yml so the PR runs only the trial, not the full suite

Author: pose

.github/workflows/compare-sdk-trial.yml

@@ -0,0 +1,30 @@
+# TEMPORARY pre-merge trial of the centralized compare_sdk workflow (pulumi/ci-mgmt#2300).
+# Runs only prerequisites + compare_sdk; run-acceptance-tests is removed in this branch.
+name: compare-sdk-trial
+on:
+  pull_request: {}
+permissions:
+  contents: read
+jobs:
+  prerequisites:
+    permissions:
+      contents: read
+      pull-requests: write
+      id-token: write
+    uses: ./.github/workflows/prerequisites.yml
+    secrets: inherit
+    with:
+      default_branch: ${{ github.event.pull_request.base.ref }}
+      is_pr: true
+      is_automated: false
+  compare_sdk:
+    needs: prerequisites
+    uses: pulumi/ci-mgmt/.github/workflows/compare_sdk.yml@pose/chores/compare-sdk-ci-workflow-2282
+    permissions:
+      contents: read
+    with:
+      version: ${{ needs.prerequisites.outputs.version }}
+      languages: '["nodejs","python","dotnet","go","java"]'
+      runs-on: ubuntu-latest
+      mise-version: 2026.3.7
+      checkout-submodules: 'false'

.github/workflows/run-acceptance-tests.yml

@@ -206,6 +206,13 @@ build_python: .make/build_python
 	@touch $@
 .PHONY: generate_python build_python
 
+# TEMPORARY (pre-merge trial): shadow-gen diff target, refs pinned to the
+# ci-mgmt PR stack. See pulumi/ci-mgmt#2300.
+compare_sdks: compare_sdk_nodejs compare_sdk_python compare_sdk_dotnet compare_sdk_go compare_sdk_java
+compare_sdk_%: .make/mise_install bin/$(CODEGEN) .make/schema | mise_env
+	GOPROXY=direct GOSUMDB=off go run github.com/pulumi/ci-mgmt/provider-ci@216aafe9c4758833f6d551549de870073ee4799f compare-sdk --language $*
+.PHONY: compare_sdks compare_sdk_nodejs compare_sdk_python compare_sdk_dotnet compare_sdk_go compare_sdk_java
+
 clean:
 	rm -rf sdk/{dotnet,nodejs,go,python}
 	rm -rf bin/*