ci: use latest control-plane main image

Signed-off-by: lucarlig <luca.carlig@ibm.com>

Author: lucarlig

.github/workflows/mcp_conformance.yml

@@ -12,7 +12,6 @@ env:
   MCP_CONFORMANCE_SOURCE_SHA: c321dd32035556e6769d3724a8ee97d87c3faaac # pragma: allowlist secret
   MCP_CONFORMANCE_SPEC_VERSION: 2026-07-28
   MCP_CONFORMANCE_SERVER_ID: 3f33286667d34b65a31c3bafd30e4c21
-  CF_CONTROLPLANE_IMAGE: ghcr.io/ibm/mcp-context-forge:latest
   CF_DATAPLANE_IMAGE: contextforge-data-plane:conformance
 
 jobs:
@@ -78,6 +77,11 @@ jobs:
         working-directory: .conformance-suite
         run: git apply ../tests/conformance/disable-flaky-progress.patch
 
+      - name: Resolve latest control-plane main image
+        env:
+          GITHUB_TOKEN: ${{ github.token }}
+        run: echo "CF_CONTROLPLANE_IMAGE=$(tests/conformance/resolve-control-plane-image.sh)" >> "${GITHUB_ENV}"
+
       - name: Pull external stack images
         env:
           MCP_CONFORMANCE_TOKEN: pull-only