Fix dependency vulnerabilities, JWT token persistence and security scanning

.github/workflows/codeql.yml

@@ -0,0 +1,43 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  schedule:
+    - cron: '23 6 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: codeql-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  analyse:
+    name: Analyse (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    permissions:
+      contents: read
+      security-events: write
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [javascript-typescript, actions]
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+
+      - name: Initialise CodeQL
+        uses: github/codeql-action/init@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: none
+          queries: security-extended
+
+      - name: Analyse
+        uses: github/codeql-action/analyze@1c5b675653bb5c22dbe9b12b556ec555138e09fd # v4
+        with:
+          category: /language:${{ matrix.language }}

README.md

@@ -8,10 +8,14 @@ never leaves the machine.
 
 That claim is enforced rather than promised: every page ships a
 `connect-src 'none'` Content Security Policy, so the browser itself refuses to
-let these tools make a network request. Tool state lives in the URL fragment,
+let these tools make a network request. Shareable tool state lives in the URL fragment,
 which browsers never send to a server, so sharing a link and uploading nothing
 are simultaneously true.
 
+JWT tokens and verification keys stay in memory and are cleared on reload. The
+JWT tool does not create or restore share links; it removes fragments from old
+links when they are opened. HMAC keys and QR payloads also stay out of URLs.
+
 ## The tools
 
 Fourteen of them, grouped into one page per area: encoding, UUID and IDs, hash