Wave 5+6: plugin ABI hardening, build modernization, ABI/security docs

Wave 5 (9 parallel agents):
- W1.1 atomic diag callback + DLL handle release on shutdown (lin)
- W2.1 unify cross-DLL heap discipline (host->alloc/free/strdup) (chen)
- W2.2 secure_zero api_key on shutdown for deepseek/anthropic (cao)
- W3 CMake modernization: target-based cxx_std_20, dstalk_boost_config
  INTERFACE lib, root-level RUNTIME_OUTPUT_DIRECTORY (hu)
- W4 GitHub Actions CI with dynamic Linux/Windows matrix (ma)
- W5.1 SSE buffer_body to cut peak memory ~67% on 32K streams (zhou)
- W6.1 LSP JSON-RPC frame parser hardened against header reordering (sun)
- W7 smoke test: copy plugin DLLs post-build + Boost.JSON src.hpp fix
  for full 9-plugin load coverage (wang)
- W8.1 README slimmed 398->92, Diataxis docs/ skeleton (deng)

Wave 6 (6 parallel agents):
- W9.1 docs/explanation: architecture + plugin-lifecycle (deng)
- W9.3 log credential leak audit (0 vulns, audit trail in
  docs/explanation/security-logging.md) (cao)
- W9.4 docs/reference/plugin-abi.md - 7-point ABI contract (lin)
- W9.6 CLI /history command + status integration (zhao)
- W9.8 plugin_loader fault tolerance: per-plugin failure no longer
  aborts dstalk_init (huang)
- W9.10 host_api unit tests: tests/host_api_test.cpp, 8 cases (liu)

CEO oversight (preexisting bugs fixed during Wave 5 verification):
- lsp_plugin.cpp:449 forward decl mismatch (int vs void)
- tools_plugin.cpp:109 missing forward decl

Multi-agent collaboration framework:
- agents/WORKFLOW.md: 6-stage protocol, two-tier governance,
  prompt template, technical constraints registry

Build: cmake --build 0 error / 0 warning. Tests: 2/2 100% pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/ci.yml

@@ -0,0 +1,75 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  # ── 动态矩阵 ──────────────────────────────────────────────
+  # PR 仅跑 Ubuntu 节省 minutes；push master 跑全矩阵 Ubuntu + Windows
+  matrix:
+    name: Determine matrix
+    runs-on: ubuntu-24.04
+    outputs:
+      os: ${{ steps.set-matrix.outputs.os }}
+    steps:
+      - id: set-matrix
+        shell: bash
+        run: |
+          if [ "${{ github.event_name }}" = "push" ] && [ "${{ github.ref }}" = "refs/heads/master" ]; then
+            echo "os=[\"ubuntu-24.04\",\"windows-2025\"]" >> "$GITHUB_OUTPUT"
+          else
+            echo "os=[\"ubuntu-24.04\"]" >> "$GITHUB_OUTPUT"
+          fi
+
+  # ── 构建 & 测试 ───────────────────────────────────────────
+  build:
+    name: ${{ matrix.os }} / ${{ matrix.build_type }}
+    needs: matrix
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ${{ fromJSON(needs.matrix.outputs.os) }}
+        build_type: [Release]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+
+      - name: Install Conan
+        run: pip install conan
+
+      - name: Cache Conan
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.conan2
+            ~/.conan2/p
+          key: ${{ runner.os }}-conan-${{ matrix.build_type }}-${{ hashFiles('deps/conanfile.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-conan-${{ matrix.build_type }}-
+            ${{ runner.os }}-conan-
+
+      - name: Install Conan dependencies
+        run: |
+          conan profile detect --force
+          conan install deps --build=missing -s build_type=${{ matrix.build_type }}
+
+      - name: Configure CMake
+        run: cmake --preset conan-release
+
+      - name: Build
+        run: cmake --build --preset conan-release --config ${{ matrix.build_type }}
+
+      - name: Test
+        run: ctest --preset conan-release -C ${{ matrix.build_type }} --output-on-failure