fix(memory): 定宽时间戳存储 + rowid 确定性排序 + 遗留数据归一化

- formatTime 改用固定 30 字节布局(9 位小数秒)，让 TEXT 列的字典序与时间序一致（RFC3339Nano 会去掉尾随零产生变宽字符串，秒内会反序）
- memory_items / project / project_chapter 的 ORDER BY 全部补 rowid 兜底，消除同 tick 打平时的顺序不确定
- 开库时幂等归一化变宽的历史值；无法解析的行原样保留，不阻塞开库
- 回归测试：变宽排序反例、同一时间戳插入序、归一化幂等与跳过

internal/runtime/memory/projectindex/chapter.go

@@ -61,8 +61,10 @@ func (s *Store) AddChapter(ctx context.Context, projectID string, ch Chapter) er
 	return nil
 }
 
-// ListChapters returns every chapter for projectID in insertion order. It returns
-// an empty (non-nil) slice when there are none; a blank projectID returns
+// ListChapters returns every chapter for projectID in insertion order
+// (created_at ASC, rowid ASC) — rowid breaks created_at ties so chapters written
+// within the same clock tick keep their insertion order. It returns an empty
+// (non-nil) slice when there are none; a blank projectID returns
 // ErrMissingProject.
 func (s *Store) ListChapters(ctx context.Context, projectID string) ([]Chapter, error) {
 	if strings.TrimSpace(projectID) == "" {
@@ -70,7 +72,7 @@ func (s *Store) ListChapters(ctx context.Context, projectID string) ([]Chapter,
 	}
 	rows, err := s.db.QueryContext(ctx, `SELECT id, project_id, title, content,
 		created_at, updated_at FROM project_chapter
-		WHERE project_id = ? ORDER BY created_at ASC, id ASC`, projectID)
+		WHERE project_id = ? ORDER BY created_at ASC, rowid ASC`, projectID)
 	if err != nil {
 		return nil, fmt.Errorf("projectindex: list chapters: %w", err)
 	}