fix(growth): CJK 记忆检索 TF-IDF 阈值过高导致注入失败

根因: SqliteStorage.find() 对 CJK 查询使用 LIKE fallback 获取候选，
但 TF-IDF 评分因 unicode61 tokenizer 不支持 CJK 而系统性地偏低，
被默认 min_similarity=0.7 阈值全部过滤掉。

修复: 检测到 CJK 查询时将阈值降至 50%（0.35），避免所有记忆被误过滤。

crates/zclaw-growth/src/storage/sqlite.rs

@@ -732,6 +732,11 @@ impl VikingStorage for SqliteStorage {
     async fn find(&self, query: &str, options: FindOptions) -> Result<Vec<MemoryEntry>> {
         let limit = options.limit.unwrap_or(50).max(20); // Fetch more candidates for reranking
 
+        // Detect CJK early — used both for LIKE fallback and similarity threshold relaxation
+        let has_cjk = query.chars().any(|c| {
+            matches!(c, '\u{4E00}'..='\u{9FFF}' | '\u{3400}'..='\u{4DBF}' | '\u{F900}'..='\u{FAFF}')
+        });
+
         // Strategy: use FTS5 for initial filtering when query is non-empty,
         // then score candidates with TF-IDF / embedding for precise ranking.
         // When FTS5 returns nothing, we return empty — do NOT fall back to
@@ -792,9 +797,6 @@ impl VikingStorage for SqliteStorage {
                     // FTS5 returned no results or failed — check if query contains CJK
                     // characters. unicode61 tokenizer doesn't index CJK, so fall back
                     // to LIKE-based search for CJK queries.
-                    let has_cjk = query.chars().any(|c| {
-                        matches!(c, '\u{4E00}'..='\u{9FFF}' | '\u{3400}'..='\u{4DBF}' | '\u{F900}'..='\u{FAFF}')
-                    });
 
                     if !has_cjk {
                         tracing::debug!(
@@ -897,9 +899,17 @@ impl VikingStorage for SqliteStorage {
                 scorer.score_similarity(query, &entry)
             };
 
-            // Apply similarity threshold
+            // Apply similarity threshold (relaxed for CJK queries since unicode61
+            // tokenizer doesn't produce meaningful TF-IDF scores for CJK text)
             if let Some(min_similarity) = options.min_similarity {
-                if semantic_score < min_similarity {
+                let threshold = if has_cjk {
+                    // CJK TF-IDF scores are systematically low due to tokenizer limitations;
+                    // use 50% of the normal threshold to avoid filtering out all results
+                    min_similarity * 0.5
+                } else {
+                    min_similarity
+                };
+                if semantic_score < threshold {
                     continue;
                 }
             }