chore(ci): 创建 GitHub Actions CI 测试矩阵

- 6 个 feature 组合并行测试（full/light/chat/chat+mcp/multi/multi+mcp）
- clippy --all-features 零警告检查
- cargo fmt --check 格式检查（stable toolchain）
- examples 编译验证（cargo test --features full）
- RUSTFLAGS=-D warnings 强制零警告
- 每个 job 设置 timeout-minutes 兜底

.github/workflows/ci.yml

@@ -0,0 +1,61 @@
+name: CI
+
+on: [push, pull_request]
+
+env:
+  RUSTFLAGS: "-D warnings"
+
+jobs:
+  test-matrix:
+    name: test (${{ matrix.features }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    strategy:
+      fail-fast: false
+      matrix:
+        features:
+          - "full"
+          - "light"
+          - "chat,provider-openai"
+          - "chat,provider-openai,tools-mcp"
+          - "multi,provider-openai"
+          - "multi,provider-openai,tools-mcp"
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          toolchain: nightly
+      - run: cargo test --no-default-features --features "${{ matrix.features }}" --lib
+
+  clippy:
+    name: clippy
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          toolchain: nightly
+      - run: cargo clippy --all-features --lib -- -D warnings
+
+  format:
+    name: fmt
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          toolchain: stable
+      - run: cargo fmt --check
+
+  examples:
+    name: examples
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          toolchain: nightly
+      - run: cargo test --features "full"