W18: context cleanup + CLI fixes + loader audit + CI matrix (W18.1-W18.4)

- W18.1 (王测+林深): Remove g_max_tokens dead API, UTF-8 bounds protection, deduplicate token counting, 0xC0/0xC1 handling, add 13 test blocks (36 checks)
- W18.2 (赵码+朱晴): Fix /context no-session error message, /status 3-state connection display
- W18.3 (曹武+徐磊): plugin_loader security audit — 9 dimensions, rating C, 1 HIGH + 2 MEDIUM findings
- W18.4 (马奔+胡桐): CI dual-platform matrix (Ubuntu clang-18 + Windows clang-cl), ccache, build timing baseline

Build 0 error, ctest 5/5 pass, metadata check clean.

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

agents/devops-ma/profile.md

@@ -32,5 +32,14 @@ performance_log:
       findings-registry.md 两条发现状态改为 FIXED。
       编译 0 error + ctest 4/4 pass。
     rating: done
+  - date: 2026-05-27
+    event: "W18.4 CI 双平台构建矩阵 + 构建时间基线"
+    detail: >
+      ci.yml 重写为 Ubuntu (clang-18) + Windows (clang-cl) 双平台矩阵。
+      新增 ci-release preset (CMakePresets.json) 作为跨平台构建配置，不硬编码编译器/工具集。
+      添加 ccache 编译缓存、Conan 依赖缓存、动态矩阵 (PR 仅 Ubuntu，push master 双平台)。
+      构建步骤集成 date +%s 计时并输出到 GITHUB_STEP_SUMMARY。
+      验证: ci.yml yaml.safe_load 通过，CMakePresets.json json.load 通过。
+    rating: done
 current_groups: []
 ---