ci(codeql): add the actions language to the analysis matrix

CodeQL's `actions` language analyses the GitHub Actions workflows
themselves — directly relevant to this PR's workflow hardening, and
closes the Hypatia `codeql_missing_actions_language` finding that the
single-language (javascript-typescript) matrix triggered.

https://claude.ai/code/session_01Jxr3Wy4ngpkbc2QwjEam82

Author: claude

.github/workflows/codeql.yml

@@ -33,6 +33,12 @@ jobs:
         include:
           - language: javascript-typescript
             build-mode: none
+          # Also analyse the GitHub Actions workflows themselves
+          # (CodeQL `actions` language) — directly relevant given the
+          # workflow-hardening in this PR, and closes the Hypatia
+          # `codeql_missing_actions_language` finding.
+          - language: actions
+            build-mode: none
 
     steps:
       - name: Checkout