ci: pin mcpp 2026.8.26.1 (#8)

The release this repository was already verified against, from its own branch
before the merge — seven repositories green, each checked to have logged
`under review: mcpp 2026.8.26.1`. This moves the pin to the published build so
the same check runs against what a user installs.

Author: Sunrisepeak

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-24.04
     timeout-minutes: 40
     env:
-      MCPP_VERSION: 2026.8.25.2
+      MCPP_VERSION: 2026.8.26.1
       XLINGS_VERSION: v2026.8.17.2
       XLINGS_NON_INTERACTIVE: '1'
       # The branch of the specification this backend is verified against. It
@@ -246,7 +246,7 @@ jobs:
       run:
         shell: bash
     env:
-      MCPP_VERSION: 2026.8.25.2
+      MCPP_VERSION: 2026.8.26.1
       XLINGS_VERSION: v2026.8.17.2
       XLINGS_NON_INTERACTIVE: '1'
     steps: