chore: Cargo warnings 清零 — 39→0 (仅剩 sqlx-postgres 外部依赖警告)

- runtime: 移除未使用的 SessionId/Datelike import，修复 unused variable
- intelligence: 模块级 #![allow(dead_code)] 抑制 Hermes 预留代码警告
- mcp.rs/persist.rs/nl_schedule.rs: 标注 #[allow(dead_code)] 保留接口

crates/zclaw-runtime/src/middleware/data_masking.rs

@@ -130,7 +130,7 @@ impl DataMasker {
         fn recover_read<T>(lock: &RwLock<T>) -> std::sync::LockResult<std::sync::RwLockReadGuard<'_, T>> {
             match lock.read() {
                 Ok(guard) => Ok(guard),
-                Err(e) => {
+                Err(_e) => {
                     tracing::warn!("[DataMasker] RwLock poisoned during read, recovering");
                     // Poison error still gives us access to the inner guard
                     lock.read()
@@ -141,7 +141,7 @@ impl DataMasker {
         fn recover_write<T>(lock: &RwLock<T>) -> std::sync::LockResult<std::sync::RwLockWriteGuard<'_, T>> {
             match lock.write() {
                 Ok(guard) => Ok(guard),
-                Err(e) => {
+                Err(_e) => {
                     tracing::warn!("[DataMasker] RwLock poisoned during write, recovering");
                     lock.write()
                 }