fix(ci): move linter workflow into .github so GitHub actually runs it

.github/workflows/linter.yml

@@ -0,0 +1,38 @@
+---
+name: Lint Code Base
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+  statuses: write
+
+jobs:
+  run-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Lint Code Base
+        uses: super-linter/super-linter@v7
+        env:
+          DEFAULT_BRANCH: main
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          VALIDATE_ALL_CODEBASE: false
+          # Naming any validator puts super-linter in opt-in mode, so only these
+          # three run. Leaving it on the default (every validator it can detect)
+          # fails this repo: jscpd uses a 0% duplicate threshold and flags the
+          # .cjs/.js module twins that CLAUDE.md requires, and checkov flags the
+          # workflows' missing permissions blocks. Bash is deliberately absent —
+          # shellcheck reports 52 findings across bin/ and test/, which is a
+          # cleanup of its own, not a merge gate.
+          VALIDATE_GITHUB_ACTIONS: true
+          VALIDATE_GITLEAKS: true
+          VALIDATE_YAML: true