feat: add version preview job to PR workflow

.github/workflows/pr.yml

@@ -11,6 +11,37 @@ jobs:
       - uses: ./.github/actions/setup
       - run: mise run ci-check
 
+  version-preview:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+          fetch-tags: true
+      - uses: ./.github/actions/setup
+      - name: Preview next version and changelog
+        run: |
+          LEVEL=$(convco version --bump --label)
+          NEXT=$(convco version --bump)
+
+          {
+            echo "## Version Preview"
+            echo ""
+
+            if [ "$LEVEL" = "release" ]; then
+              echo "No version bump needed (no changes since last release)."
+            else
+              echo "**Bump level:** \`${LEVEL}\`"
+              echo ""
+              echo "**Next version:** \`${NEXT}\`"
+              echo ""
+              echo "### Changelog"
+              echo '```'
+              convco changelog --unreleased || true
+              echo '```'
+            fi
+          } >> "$GITHUB_STEP_SUMMARY"
+
   build:
     uses: ./.github/workflows/_build.yml
     with: