ci: add missing ctags runtime dependencies for macOS and libxml2

The ctags binary is dynamically linked against jansson, libyaml, pcre2
(macOS) and libxml2 (Linux). Without these on the test runner, ctags
fails at runtime with dylib/so not found errors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: clemlesne

.github/workflows/ci.yml

@@ -179,7 +179,11 @@ jobs:
 
       - name: Install ctags runtime dependencies (Linux)
         if: runner.os == 'Linux'
-        run: sudo apt-get update && sudo apt-get install -y libjansson4 libyaml-0-2
+        run: sudo apt-get update && sudo apt-get install -y libjansson4 libyaml-0-2 libxml2
+
+      - name: Install ctags runtime dependencies (macOS)
+        if: runner.os == 'macOS'
+        run: brew install jansson libyaml pcre2
 
       - name: Print versions
         run: |