ci: pin windows workspace leg back to mcpp 0.0.94 (temporary, mcpp#230)

mcpp 0.0.95 aborts `mcpp test --workspace` with exit 127 on windows-latest
(regression tracked in mcpp-community/mcpp#230; main@0.0.94 is green daily).
Windows consumes no 0.0.95 descriptor grammar — the compat.ffmpeg member is
cfg(linux)-gated to a no-op there — so the older floor is sound. The pin is
a per-matrix override (MCPP_EFFECTIVE); drop it once #230 is fixed.

Author: Sunrisepeak

.github/workflows/validate.yml

@@ -168,6 +168,14 @@ jobs:
             ext: zip
             mcpp: bin/mcpp.exe
             xlings: registry/bin/xlings.exe
+            # TEMPORARY: pinned back to 0.0.94 — mcpp 0.0.95 aborts
+            # `mcpp test --workspace` with exit 127 on windows-latest
+            # (mcpp-community/mcpp#230). This platform consumes no 0.0.95
+            # descriptor grammar (cfg(linux)-gated members are no-ops here),
+            # so the older floor is sound. Drop once #230 is fixed.
+            mcpp_version: "0.0.94" 
+    env:
+      MCPP_EFFECTIVE: ${{ matrix.mcpp_version || env.MCPP_VERSION }}
     steps:
       - uses: actions/checkout@v4
       - name: Restore mcpp registry cache
@@ -176,17 +184,17 @@ jobs:
           # Holds toolchains AND the built compat packages (data/xpkgs), so a
           # repeat `mcpp test` rebuilds little.
           path: ~/.mcpp/registry
-          key: mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-${{ hashFiles('pkgs/**/*.lua', 'tests/**', '.github/workflows/validate.yml') }}
+          key: mcpp-registry-${{ runner.os }}-${{ env.MCPP_EFFECTIVE }}-${{ hashFiles('pkgs/**/*.lua', 'tests/**', '.github/workflows/validate.yml') }}
           restore-keys: |
-            mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-
+            mcpp-registry-${{ runner.os }}-${{ env.MCPP_EFFECTIVE }}-
       - name: Download mcpp
         shell: bash
         env:
-          MCPP_ARCHIVE: mcpp-${{ env.MCPP_VERSION }}-${{ matrix.suffix }}.${{ matrix.ext }}
-          MCPP_ROOT: mcpp-${{ env.MCPP_VERSION }}-${{ matrix.suffix }}
+          MCPP_ARCHIVE: mcpp-${{ env.MCPP_EFFECTIVE }}-${{ matrix.suffix }}.${{ matrix.ext }}
+          MCPP_ROOT: mcpp-${{ env.MCPP_EFFECTIVE }}-${{ matrix.suffix }}
         run: |
           curl -L -fsS -o "$MCPP_ARCHIVE" \
-            "https://github.com/mcpp-community/mcpp/releases/download/v${MCPP_VERSION}/${MCPP_ARCHIVE}"
+            "https://github.com/mcpp-community/mcpp/releases/download/v${MCPP_EFFECTIVE}/${MCPP_ARCHIVE}"
           case "$MCPP_ARCHIVE" in
             *.zip) powershell -NoProfile -Command "Expand-Archive -Force -Path '${MCPP_ARCHIVE}' -DestinationPath '.'" ;;
             *)     tar -xzf "$MCPP_ARCHIVE" ;;
@@ -233,15 +241,17 @@ jobs:
   imgui-module:
     runs-on: ubuntu-latest
     timeout-minutes: 60
+    env:
+      MCPP_EFFECTIVE: ${{ matrix.mcpp_version || env.MCPP_VERSION }}
     steps:
       - uses: actions/checkout@v4
       - name: Restore mcpp registry cache
         uses: actions/cache@v4
         with:
           path: ~/.mcpp/registry
-          key: mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-${{ hashFiles('pkgs/**/*.lua', 'tests/**', '.github/workflows/validate.yml') }}
+          key: mcpp-registry-${{ runner.os }}-${{ env.MCPP_EFFECTIVE }}-${{ hashFiles('pkgs/**/*.lua', 'tests/**', '.github/workflows/validate.yml') }}
           restore-keys: |
-            mcpp-registry-${{ runner.os }}-${{ env.MCPP_VERSION }}-
+            mcpp-registry-${{ runner.os }}-${{ env.MCPP_EFFECTIVE }}-
       - name: Download mcpp
         run: |
           curl -L -fsS -o mcpp.tar.gz \