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-protocols/src/lib.rs

@@ -1,20 +1,15 @@
 //! ZCLAW Protocols
 //!
 //! Protocol support for MCP (Model Context Protocol) and A2A (Agent-to-Agent).
-//!
-//! A2A is gated behind the `a2a` feature flag (reserved for future multi-agent scenarios).
-//! MCP is always available as a framework for tool integration.
 
 mod mcp;
 mod mcp_types;
 mod mcp_tool_adapter;
 mod mcp_transport;
-#[cfg(feature = "a2a")]
 mod a2a;
 
 pub use mcp::*;
 pub use mcp_types::*;
 pub use mcp_tool_adapter::*;
 pub use mcp_transport::*;
-#[cfg(feature = "a2a")]
 pub use a2a::*;