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/designer-zhu/profile.md

@@ -24,5 +24,9 @@ performance_log:
   - date: 2026-05-27
     event: "W10.3: 创建 agents/PROMPT_TEMPLATE.md 子代理 prompt 模板（约 170 行），含骨架+6 反模式+1 正模式+CEO 4 步检查。统一字数 250 字，WORKFLOW.md §9 追加迁移链接"
     rating: completed
-current_groups: []
+  - date: 2026-05-27
+    event: "W18.2: 协作赵码完成 CLI 命令分发修复 — 定义 /context 无 session 错误文案 No active session，定义 /status 连接状态三态交互语义（已连接/插件已加载模型未配置/未连接），编译 0 error + ctest 4/4 pass"
+    rating: A
+current_groups:
+  - grp-cli-ux
 ---