Create custom CodeQL workflow (#334739)

* Create custom CodeQL workflow

* build: Exclude nested esbuild scripts from CodeQL

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* build: Align CodeQL coverage with packaged files

Keep Markdown build/test scripts out of the extension package and restore scanning of the shipped chat-library postinstall script.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: Expand CodeQL release coverage and scope permissions

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/workflows/codeql.yml

@@ -0,0 +1,51 @@
+name: CodeQL
+
+on:
+  push:
+    branches:
+      - main
+      - 'release/**/*'
+  pull_request:
+    branches:
+      - main
+      - 'release/**/*'
+  schedule:
+    - cron: '17 19 * * 6'
+
+permissions: {}
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      packages: read
+      security-events: write
+    strategy:
+      fail-fast: false
+      matrix:
+        # Other detected languages occur only in test fixtures or build tooling.
+        include:
+          - language: javascript-typescript
+            build-mode: none
+          - language: rust
+            build-mode: none
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+          dependency-caching: true
+          config-file: ./.github/codeql/codeql-config.yml
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@cdf488f595d80d6e07e03d4674febd5ab45fa938 # v4.37.9
+        with:
+          category: /language:${{ matrix.language }}