fix: 审计后续 3 项修复 — 残留清理 + FTS5 CJK + HTTP 大小限制

1. Shell Hands 残留清理 (3处):
   - message.rs: 移除过时的 zclaw_hands::slideshow 注释
   - user_profiler.rs: slideshow 偏好改为 RecentTopic
   - handStore.test.ts: 移除 speech mock 数据 (3→2)

2. zclaw-growth FTS5 CJK 查询修复:
   - sanitize_fts_query CJK 路径从精确短语改为 token OR 组合
   - "Rust 编程" → "rust" OR "编程" (之前是 "rust 编程" 精确匹配)
   - 修复 test_memory_lifecycle + test_semantic_search_ranking

3. WASM HTTP 响应大小限制:
   - Content-Length 预检 + 读取后截断 (1MB 上限)
   - read_to_string 改为显式错误处理

651 测试全通过，0 失败。

crates/zclaw-types/src/message.rs

@@ -116,7 +116,6 @@ impl Message {
 
 /// Canonical LLM message content block. Used for agent conversation messages.
 /// See also: zclaw_runtime::driver::ContentBlock (LLM driver response subset),
-/// zclaw_hands::slideshow::ContentBlock (presentation rendering),
 /// zclaw_protocols::mcp_types::ContentBlock (MCP protocol wire format).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(tag = "type", rename_all = "snake_case")]