ci: filter hermesCommitAtMergeBase stdout to extract only commit hash

The hermesLog() calls write to stdout and were captured by the
shell command substitution, corrupting the GITHUB_OUTPUT format.
Filter to just the 40-char hex commit hash.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Saadnajmi

.github/workflows/microsoft-build-spm.yml

@@ -34,7 +34,7 @@ jobs:
         id: resolve
         working-directory: packages/react-native
         run: |
-          COMMIT=$(node -e "const {hermesCommitAtMergeBase} = require('./scripts/ios-prebuild/hermes'); console.log(hermesCommitAtMergeBase().commit);")
+          COMMIT=$(node -e "const {hermesCommitAtMergeBase} = require('./scripts/ios-prebuild/hermes'); console.log(hermesCommitAtMergeBase().commit);" 2>&1 | grep -E '^[0-9a-f]{40}$')
           echo "hermes-commit=$COMMIT" >> "$GITHUB_OUTPUT"
           echo "Resolved Hermes commit: $COMMIT"