ci: add Rust CI and Dependabot configuration

.github/dependabot.yml

@@ -0,0 +1,31 @@
+# Weekly dependency updates; grouped so the agent receives fewer, reviewable PRs.
+version: 2
+updates:
+  - package-ecosystem: cargo
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "04:00"
+      timezone: Asia/Shanghai
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: deps
+    groups:
+      patch-and-minor:
+        patterns: ["*"]
+        update-types: ["patch", "minor"]
+
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+      day: monday
+      time: "04:00"
+      timezone: Asia/Shanghai
+    open-pull-requests-limit: 3
+    commit-message:
+      prefix: ci
+    groups:
+      actions:
+        patterns: ["*"]

.github/workflows/ci.yml

@@ -0,0 +1,41 @@
+# RayRAG CI — format check plus a compile check of the JSON-index build.
+# The default zvec build needs the native libzvec_c_api.so, which is not
+# available on hosted runners, so CI validates the postgres-only feature set.
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    name: Rust (fmt + check, JSON-index build)
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+
+      - name: Cache cargo
+        uses: Swatinem/rust-cache@v2
+
+      - name: Format check
+        run: cargo fmt --all -- --check
+
+      - name: Compile check (no zvec native dependency)
+        run: cargo check --locked --no-default-features --features postgres-backend