W20: Tool Calling 闭环 + Stream+Tools + 回归测试 + session auto-save + ASan CI (W20.1-W20.6)

- W20.1: CLI tool_calls→execute→result→re-call 循环（5轮上限）
- W20.2: deepseek 流式 tool_calls 增量解析（configure 缓存，无 ABI break）
- W20.3: plugin_loader 回归测试 5 块 32 断言（路径/原子性/mock 日志）
- W20.4: plugin_loader ABI 契约校验（name/version/on_init 字段验证）
- W20.5: ASan/UBSan CMake preset + CI sanitizer job（PR-only Linux）
- W20.6: session auto-save（on_shutdown 写 %APPDATA%/dstalk/session.json）

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -160,3 +160,67 @@ jobs:
           echo "|----------|----------|-----------|" >> $GITHUB_STEP_SUMMARY
           echo "| ${{ matrix.os }} | ${{ (runner.os == 'Linux' && 'clang-18') || 'clang-cl' }} | ${DURATION}s |" >> $GITHUB_STEP_SUMMARY
           echo "CI build: ${{ matrix.os }} / ${{ (runner.os == 'Linux' && 'clang-18') || 'clang-cl' }} wall time ${DURATION}s"
+
+  # ── Sanitizer (PR-only, Linux clang-18, no ccache) ───────
+  sanitize:
+    name: Sanitizer (ASan+UBSan) / ubuntu-24.04
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-24.04
+
+    steps:
+      # ── 1. 源码检出 ──────────────────────────────────────
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      # ── 2. 工具链 (clang-18) ─────────────────────────────
+      - name: Install toolchain (Ubuntu)
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y -qq clang-18 ninja-build
+          echo "CC=clang-18" >> $GITHUB_ENV
+          echo "CXX=clang++-18" >> $GITHUB_ENV
+
+      # ── 3. Python + Conan ─────────────────────────────────
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - name: Install Conan
+        run: pip install conan
+
+      # ── 4. Conan 依赖缓存 ─────────────────────────────────
+      - name: Cache Conan
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.conan2
+            ~/.conan2/p
+          key: ${{ runner.os }}-conan-Release-${{ hashFiles('deps/conanfile.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-conan-Release-
+            ${{ runner.os }}-conan-
+
+      # ── 5. Conan 依赖安装 ─────────────────────────────────
+      - name: Install Conan dependencies
+        shell: bash
+        run: |
+          conan profile detect --force
+          conan install deps --build=missing -s build_type=Release
+
+      # ── 6. CMake 配置 ─────────────────────────────────────
+      - name: Configure CMake (Sanitizer)
+        shell: bash
+        run: cmake --preset ci-sanitize
+
+      # ── 7. 构建 ───────────────────────────────────────────
+      - name: Build (Sanitizer)
+        shell: bash
+        run: cmake --build --preset ci-sanitize
+
+      # ── 8. 测试 ──────────────────────────────────────────
+      - name: Test (Sanitizer)
+        shell: bash
+        run: ctest --preset ci-sanitize --output-on-failure