diff --git a/.github/workflows/artifact-cleanup.yml b/.github/workflows/artifact-cleanup.yml
new file mode 100644
index 0000000..234af34
--- /dev/null
+++ b/.github/workflows/artifact-cleanup.yml
@@ -0,0 +1,120 @@
+name: Artifact cleanup
+
+# Deletes GitHub Actions artifacts older than a threshold so storage doesn't
+# accumulate and trip the account-wide quota.
+#
+# Three triggers:
+#   - schedule: Monday 06:00 UTC, same slot as branch-protection-sync,
+#     security, and dependabot for weekly-governance clustering.
+#   - workflow_dispatch: on-demand cleanup with inputs for threshold +
+#     dry-run safety.
+#   - push: not wired — cleanup doesn't need to fire on code changes.
+#
+# Uses the default GITHUB_TOKEN (built-in `actions: write` scope is
+# sufficient for artifact deletion — no PAT needed). The scheduled run
+# uses the hard-coded default (7 days, live delete); manual runs default
+# to dry-run for safety.
+
+on:
+  schedule:
+    - cron: "0 6 * * 1"
+  workflow_dispatch:
+    inputs:
+      days_to_keep:
+        description: "Delete artifacts older than this many days"
+        required: true
+        default: "7"
+      dry_run:
+        description: "List only, no deletion (safe to flip to false when ready)"
+        type: boolean
+        default: true
+
+permissions:
+  actions: write   # for artifact deletion
+  contents: read
+
+concurrency:
+  group: artifact-cleanup
+  cancel-in-progress: false
+
+jobs:
+  cleanup:
+    name: Prune old artifacts
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+
+      - name: Compute threshold
+        id: threshold
+        env:
+          DAYS: ${{ inputs.days_to_keep || '7' }}
+        run: |
+          days="${DAYS}"
+          threshold_secs=$(( days * 86400 ))
+          echo "days=${days}"           >> "$GITHUB_OUTPUT"
+          echo "secs=${threshold_secs}" >> "$GITHUB_OUTPUT"
+          echo "::notice::Pruning artifacts older than ${days} day(s)."
+
+      - name: List candidates
+        id: list
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          THRESHOLD_SECS: ${{ steps.threshold.outputs.secs }}
+        run: |
+          gh api --paginate \
+            "/repos/${GITHUB_REPOSITORY}/actions/artifacts?per_page=100" \
+            --jq ".artifacts[]
+              | select((now - (.created_at | fromdateiso8601)) > ${THRESHOLD_SECS})
+              | [.id, .created_at,
+                 ((.size_in_bytes/1024/1024*100|floor)/100|tostring),
+                 (.workflow_run.name // \"<unknown>\"),
+                 .name]
+              | @tsv" \
+            > candidates.tsv
+          count=$(wc -l < candidates.tsv | tr -d ' ')
+          echo "count=${count}" >> "$GITHUB_OUTPUT"
+          echo "::notice::Found ${count} artifact(s) older than ${{ steps.threshold.outputs.days }} day(s)."
+
+      - name: Summary (candidates)
+        if: always()
+        run: |
+          {
+            echo "### Artifact cleanup — dry_run=${{ inputs.dry_run || 'false (scheduled)' }}"
+            echo ""
+            echo "**Threshold:** older than ${{ steps.threshold.outputs.days }} day(s)"
+            echo "**Matched:** ${{ steps.list.outputs.count }} artifact(s)"
+            echo ""
+            echo "| id | created_at | size (MB) | workflow | name |"
+            echo "|---|---|---|---|---|"
+            awk -F'\t' '{ printf "| %s | %s | %s | %s | %s |\n", $1, $2, $3, $4, $5 }' \
+              candidates.tsv || true
+          } >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Delete (skipped when dry_run=true)
+        if: ${{ inputs.dry_run == false || inputs.dry_run == 'false' || github.event_name == 'schedule' }}
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Individual 404s are expected — an artifact can expire between the
+          # list call and the delete call. A mixed outcome still passes. Only
+          # the every-attempt-failed signal escalates (token lost
+          # `actions: write`, API rate-limit, network flake).
+          deleted=0
+          failed=0
+          while IFS=$'\t' read -r id _rest; do
+            if [ -n "${id}" ]; then
+              if gh api -X DELETE "/repos/${GITHUB_REPOSITORY}/actions/artifacts/${id}" > /dev/null 2>&1; then
+                deleted=$((deleted + 1))
+              else
+                echo "::warning::failed to delete artifact ${id}"
+                failed=$((failed + 1))
+              fi
+            fi
+          done < candidates.tsv
+          echo "::notice::Deleted ${deleted} artifact(s); ${failed} failure(s)."
+          echo "" >> "$GITHUB_STEP_SUMMARY"
+          echo "**Deleted:** ${deleted} artifact(s); ${failed} failure(s)." >> "$GITHUB_STEP_SUMMARY"
+          if [ "${failed}" -gt 0 ] && [ "${deleted}" -eq 0 ]; then
+            echo "::error::All ${failed} delete attempts failed. Check token scope (actions: write) or API rate limits."
+            exit 1
+          fi
diff --git a/.github/workflows/branch-protection.yml b/.github/workflows/branch-protection.yml
new file mode 100644
index 0000000..8da4bef
--- /dev/null
+++ b/.github/workflows/branch-protection.yml
@@ -0,0 +1,95 @@
+name: Branch protection sync
+
+# Applies the declarative branch-protection configuration in
+# .github/branch-protection/*.json to main and develop. See that directory's
+# README for rationale and the trigger matrix.
+
+on:
+  schedule:
+    # Weekly drift re-assertion, Monday 06:00 UTC. Same slot as the security
+    # workflow and Dependabot for governance-activity clustering.
+    - cron: "0 6 * * 1"
+  workflow_dispatch:
+  push:
+    branches: [main]
+    paths:
+      - .github/branch-protection/**
+      - .github/workflows/branch-protection.yml
+
+permissions:
+  contents: read
+
+# Serialise concurrent applies. A scheduled run, a manual dispatch, and a
+# push landing around the same time could otherwise race on the same PUT.
+# cancel-in-progress: false — never interrupt a protection apply mid-flight.
+concurrency:
+  group: branch-protection-sync
+  cancel-in-progress: false
+
+jobs:
+  apply:
+    name: Apply ${{ matrix.branch }} protection
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        branch: [main, develop]
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+
+      - name: Verify token is configured
+        env:
+          GH_TOKEN: ${{ secrets.BRANCH_PROTECTION_TOKEN }}
+        run: |
+          if [ -z "$GH_TOKEN" ]; then
+            echo "::error::BRANCH_PROTECTION_TOKEN secret is not set."
+            echo "::error::See docs/DEVELOPMENT.md#branch-protection-sync-setup."
+            exit 1
+          fi
+
+      - name: Snapshot current protection (before)
+        env:
+          GH_TOKEN: ${{ secrets.BRANCH_PROTECTION_TOKEN }}
+        run: |
+          # May 404 if protection doesn't exist yet (first run). That's fine.
+          gh api \
+            -H "Accept: application/vnd.github+json" \
+            "/repos/${{ github.repository }}/branches/${{ matrix.branch }}/protection" \
+            > before.json 2>/dev/null || echo '{"note": "no protection set before run"}' > before.json
+
+      - name: Apply ${{ matrix.branch }} protection
+        env:
+          GH_TOKEN: ${{ secrets.BRANCH_PROTECTION_TOKEN }}
+        run: |
+          gh api \
+            --method PUT \
+            -H "Accept: application/vnd.github+json" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            "/repos/${{ github.repository }}/branches/${{ matrix.branch }}/protection" \
+            --input ".github/branch-protection/${{ matrix.branch }}.json"
+
+      - name: Snapshot current protection (after)
+        env:
+          GH_TOKEN: ${{ secrets.BRANCH_PROTECTION_TOKEN }}
+        run: |
+          gh api \
+            -H "Accept: application/vnd.github+json" \
+            "/repos/${{ github.repository }}/branches/${{ matrix.branch }}/protection" \
+            > after.json
+
+      - name: Summary (with before → after diff)
+        if: always()
+        run: |
+          {
+            echo "### Branch protection: ${{ matrix.branch }}"
+            echo ""
+            echo "**Config source:** \`.github/branch-protection/${{ matrix.branch }}.json\`"
+            echo ""
+            echo "**Before → after diff** (empty block = no drift was present):"
+            echo ""
+            echo '```diff'
+            diff -u before.json after.json || true
+            echo '```'
+            echo ""
+            echo "Review current state at https://github.com/${{ github.repository }}/settings/branches"
+          } >> "$GITHUB_STEP_SUMMARY"
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
new file mode 100644
index 0000000..a06c133
--- /dev/null
+++ b/.github/workflows/codeql.yml
@@ -0,0 +1,55 @@
+# CodeQL — placeholder (disabled).
+#
+# CodeQL on a private personal repo requires GitHub Advanced Security (GHAS),
+# which is only available on Enterprise plans. When this repo either:
+#   (a) becomes public, or
+#   (b) gains a code-scanning subscription (GHAS or equivalent),
+# re-activate by replacing the `on:` block below with:
+#
+#   on:
+#     push:
+#       branches: [main, develop]
+#     pull_request:
+#       branches: [main, develop]
+#     schedule:
+#       - cron: "0 6 * * 1"
+#
+# Until then the workflow is manual-trigger-only (workflow_dispatch) so it
+# does not fire on pushes/PRs and does not pollute CI with guaranteed
+# failures.
+
+name: CodeQL
+
+on:
+  workflow_dispatch:
+
+permissions:
+  actions: read
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: python
+            build-mode: none
+          - language: javascript-typescript
+            build-mode: none
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{ matrix.language }}"