ci: add dependency security audit and Dependabot

.github/dependabot.yml

@@ -0,0 +1,34 @@
+version: 2
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "04:00"
+      timezone: "UTC"
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: "chore(deps)"
+    groups:
+      cargo-minor-and-patch:
+        patterns:
+          - "*"
+        update-types:
+          - "minor"
+          - "patch"
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "04:00"
+      timezone: "UTC"
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: "ci(deps)"
+    groups:
+      github-actions:
+        patterns:
+          - "*"

.github/workflows/security-audit.yml

@@ -0,0 +1,40 @@
+name: Security audit
+
+on:
+  push:
+  pull_request:
+  schedule:
+    # Weekly, Mondays at 04:17 UTC
+    - cron: "17 4 * * 1"
+
+permissions:
+  contents: read
+
+concurrency:
+  group: security-audit-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  audit:
+    name: cargo audit
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4.4.0
+        with:
+          persist-credentials: false
+
+      - name: Install stable Rust toolchain
+        uses: dtolnay/rust-toolchain@b725eda525362e7cf34af9a7243cac1e3f01a7ec # stable
+        with:
+          toolchain: stable
+
+      - name: Install cargo-audit
+        run: cargo install cargo-audit --version 0.22.2 --locked
+
+      # api does not commit a Cargo.lock, so generate one for scanning only.
+      - name: Generate lockfile
+        run: cargo generate-lockfile
+
+      - name: Audit dependencies
+        run: cargo audit --deny warnings

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## 2026-10-24 — Dependency security automation
+
+- Added `.github/workflows/security-audit.yml`: runs `cargo audit` 0.22.2 with `--deny warnings` on push, pull request and a weekly schedule. The workflow generates a temporary lockfile before auditing because the workspace does not version one.
+- Added weekly Dependabot updates for Cargo dependencies and GitHub Actions (`open-pull-requests-limit: 5`, minor/patch grouped).
+- Actions are pinned by commit SHA and checkouts do not persist credentials. No crate source or public API changed; a generated lockfile audits clean (16 crates, 0 vulnerabilities, 0 warnings).
+
 ## 2026-09-12
 - Added `xfetch-guest-api`: host-call bridge for WebAssembly core-module guests (`host_call`, `http_request`, `exec`, `log`, `protocol_version`) plus the `xfetch_alloc`/`xfetch_free` exports the host needs.
 - Added `wit/xfetch-runtime.wit`: the component-model contract with `plugin`, `effect` and `extension` worlds and the typed `fetch`/`exec`/`log`/`protocol-version` host interface.