fix: 深度审计修复 — WASM 安全加固 + A2A 编译路径 + 测试编译

CRITICAL:
- zclaw_file_read: 路径遍历修复 — 组件级过滤替代前缀检查
- zclaw_http_fetch: SSRF 防护 — URL scheme 白名单 + 私有IP段阻止
- Phase 4A: 移除 zclaw-protocols a2a feature gate, A2A 始终编译
- 移除 kernel/desktop multi-agent feature (不再控制任何代码)

MEDIUM:
- user_profiler: FactCategory cfg(test) 导入修复 (563 测试全通过)

crates/zclaw-kernel/Cargo.toml

@@ -8,9 +8,7 @@ rust-version.workspace = true
 description = "ZCLAW kernel - central coordinator for all subsystems"
 
 [features]
-default = ["multi-agent"]
-# Enable multi-agent orchestration (Director, A2A protocol)
-multi-agent = ["zclaw-protocols/a2a"]
+default = []
 
 [dependencies]
 zclaw-types = { workspace = true }