[temp] probe 885: an incremental rebuild of touched interfaces after the cross build (copy_atomic settle path)

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>

Author: Sunrisepeak

.github/workflows/probe-885.yml

@@ -30,7 +30,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rep: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]
+        rep: [1, 2, 3]
     steps:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/bootstrap-mcpp
@@ -61,6 +61,23 @@ jobs:
           rc=${PIPESTATUS[0]}
           echo "rc=$rc seconds=$(( $(date +%s) - start ))" | tee "$RUNNER_TEMP/cross.rc"
           exit $rc
+      - name: "Incremental: touch module interfaces, rebuild (settle path)"
+        if: always() && steps.cross.outcome == 'success'
+        shell: bash
+        run: |
+          export MCPP_VENDORED_XLINGS="$XLINGS_BIN"
+          # An unchanged interface recompiles to an equivalent BMI, which the
+          # split schedule settles by restoring the previous BMI (copy_atomic).
+          files=$(git ls-files 'src/*.cppm' | head -5)
+          echo "touched: $files"
+          touch $files
+          set +e
+          "$MCPP_SELF" build --target x86_64-linux-musl 2>&1 | tee "$RUNNER_TEMP/incremental.log"
+          rc=${PIPESTATUS[0]}
+          echo "incremental rc=$rc" | tee -a "$RUNNER_TEMP/cross.rc"
+          grep -E "^mcpp: |^error: |^failed: " "$RUNNER_TEMP/incremental.log" | head -20 >> "$GITHUB_STEP_SUMMARY"
+          echo "incremental rc=$rc" >> "$GITHUB_STEP_SUMMARY"
+          exit $rc
       - name: Summarise
         if: always()
         shell: bash
@@ -73,4 +90,5 @@ jobs:
             ${{ runner.temp }}/okprobe
             ${{ runner.temp }}/cross.log
             ${{ runner.temp }}/cross.rc
+            ${{ runner.temp }}/incremental.log
           retention-days: 14