ci: improve workflow determinism and security scanning

- Add --language=shellspec flag to tree-sitter parse for deterministic grammar selection
- Add C++ language to CodeQL analysis to scan src/scanner.c for security issues

Addresses PR #1 review comments from CodeRabbit.

.github/workflows/codeql.yml

@@ -24,7 +24,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        language: ['actions,javascript'] # Add languages used in your actions
+        language: ['actions,javascript', 'cpp'] # Add languages used in your actions
 
     steps:
       - name: Checkout repository

.github/workflows/test.yml

@@ -140,7 +140,7 @@ jobs:
           End
           EOF
 
-          npx tree-sitter parse test_sample.shellspec --quiet || {
+          npx tree-sitter parse --language=shellspec test_sample.shellspec --quiet || {
             echo "❌ Parser failed on sample ShellSpec code"
             exit 1
           }