Harden lint workflow and add GitHub mirror support

.github/workflows/lint-and-security.yml

@@ -0,0 +1,79 @@
+name: Lint & Security
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  precommit-and-security:
+    name: lint-and-security
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+
+      - name: Install Poetry
+        run: pip install "poetry>=2,<3"
+
+      - name: Install dev dependencies (lockfile-pinned pre-commit)
+        run: poetry install --with dev --no-root
+
+      - name: Run pre-commit hooks
+        run: poetry run pre-commit run --all-files --color always
+
+      - name: Install pip-audit
+        run: pip install "pip-audit==2.10.1"
+
+      - name: Audit dependencies (Poetry lockfile)
+        run: |
+          set -euo pipefail
+
+          poetry self add poetry-plugin-export
+          poetry export -f requirements.txt --without-hashes -o requirements-audit.txt
+
+          # pip-audit exits non-zero for ANY vulnerability; capture the report, then gate below.
+          pip-audit --no-deps -r requirements-audit.txt -f json -o pip-audit.json || true
+
+          echo "Fixable vulnerabilities:"
+          jq -r '
+            .dependencies[]?
+            | select(has("vulns"))
+            | . as $d
+            | .vulns[]
+            | select((.fix_versions | length) > 0)
+            | "\($d.name)@\($d.version) -> \(.id) [fix: \(.fix_versions | join(", "))]"
+          ' pip-audit.json
+
+          echo
+          echo "All reported vulnerabilities:"
+          jq -r '
+            .dependencies[]?
+            | select(has("vulns"))
+            | . as $d
+            | .vulns[]
+            | "\($d.name)@\($d.version) -> \(.id) [fix: \(if (.fix_versions | length) > 0 then (.fix_versions | join(", ")) else "none" end)]"
+          ' pip-audit.json
+
+          # Fail only on fixable findings (mirrors the Grype policy in security-scan.yml).
+          # The type guard ensures a crashed/empty report fails rather than silently passing.
+          jq -e '
+            (.dependencies | type) == "array"
+            and
+            ( [ .dependencies[] | (.vulns // [])[] | select((.fix_versions | length) > 0) ] | length == 0 )
+          ' pip-audit.json