docs(comments): 注释中文化 · internal/runtime/memory（31 文件，纯替换）

- 只翻注释/文档字符串：820 增 / 820 删 严格 1:1；剥掉整行注释与行尾注释尾巴后，
  逐文件与 HEAD 比对「代码部分差异 = 0」；裁决/design 编号计数逐项与 HEAD 一致
- 保留可执行 SQL 样例、SQLite 报错原文、pgvector/HNSW/ANN/BLOB 等技术词原文
- 复核：go build 绿 + memory/projectindex/vector 三包测试绿；gofmt 仅剩 2 个既有未格式化文件（改动前即如此，未顺手修）

internal/runtime/memory/decay_test.go

@@ -19,12 +19,12 @@ func TestRetriever_DecayFactor_久未使用降权(t *testing.T) {
 		want        float64
 	}{
 		{name: "fresh keeps full weight", updatedAt: now, decayWeight: 1.0, want: 1.0},
-		// Default half-life is 30 days: 60 days ago = 2 half-lives = 2^-2.
+		// 默认半衰期为 30 天：60 天前 = 2 个半衰期 = 2^-2。
 		{name: "two half-lives halves twice", updatedAt: now.Add(-60 * 24 * time.Hour), decayWeight: 1.0, want: 0.25},
-		// Lower base decay_weight scales the whole curve down.
+		// 较低的基础 decay_weight 会整体压低曲线。
 		{name: "low decay_weight scales down", updatedAt: now, decayWeight: 0.5, want: 0.5},
 		{name: "low weight plus age compounds", updatedAt: now.Add(-60 * 24 * time.Hour), decayWeight: 0.5, want: 0.125},
-		// A future timestamp must not boost above the base weight.
+		// 未来时间戳不得把得分抬到基础权重以上。
 		{name: "future timestamp clamps to zero", updatedAt: now.Add(time.Hour), decayWeight: 1.0, want: 1.0},
 	}
 	for _, tt := range tests {
@@ -48,21 +48,21 @@ func TestRetriever_Retrieve_DecayWeight_降权(t *testing.T) {
 	s := newTestStore(t)
 
 	now := time.Now().UTC()
-	// A fresh item but with a near-zero decay_weight (design: 用户可削弱某记忆).
+	// 一条新鲜但 decay_weight 近乎零的条目（design：用户可削弱某记忆）。
 	addItem(t, s, MemoryItem{
 		PersonaID: "persona.a", Content: "低权重但新鲜", UpdatedAt: now,
 		DecayWeight: 0.1, Scope: ScopePersona, Kind: KindWorldEvent,
 	})
-	// A slightly older item with a full decay_weight.
+	// 稍有历史、但 decay_weight 满额的条目。
 	addItem(t, s, MemoryItem{
 		PersonaID: "persona.a", Content: "权重高稍旧", UpdatedAt: now.Add(-time.Hour),
 		DecayWeight: 1.0, Scope: ScopePersona, Kind: KindWorldEvent,
 	})
 
 	r := NewRetriever(s)
-	// A blank query matches nothing, so ordering is driven by the decay factor
-	// (decay_weight × time decay) alone: the low-weight fresh item must fall
-	// below the full-weight slightly-older item.
+	// query 为空时无任何命中，因此排序完全由衰减因子
+	// （decay_weight × 时间衰减）驱动：低权重的新条目必须
+	// 排在满权重、稍旧的条目之后。
 	results, err := r.Retrieve(ctx, "persona.a", "", 10)
 	if err != nil {
 		t.Fatalf("Retrieve: %v", err)