fix: improve doc link navigation and tree display

- Fix link resolution with proper relative/absolute path handling
- Improve link styling with underline decoration
- Hide leaf nodes from tree, only show directories
- Fix log file path for packaged app

docs/api/memory/pool-allocator/get-free-block-count.md

@@ -0,0 +1,40 @@
+# PoolAllocator::GetFreeBlockCount
+
+```cpp
+size_t GetFreeBlockCount() const;
+```
+
+返回当前空闲块的的数量。每次 `Allocate` 成功后减 1，每次 `Free` 后加 1。
+
+**参数：** 无
+
+**返回：** 当前可分配的空闲块数量
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+#include <XCEngine/Memory/PoolAllocator.h>
+
+PoolAllocator pool(sizeof(int), 100);
+
+size_t initial = pool.GetFreeBlockCount(); // 100
+
+void* blocks[10];
+for (int i = 0; i < 10; ++i) {
+    blocks[i] = pool.Allocate();
+}
+
+size_t after = pool.GetFreeBlockCount(); // 90
+
+for (int i = 0; i < 5; ++i) {
+    pool.Free(blocks[i]);
+}
+
+size_t final = pool.GetFreeBlockCount(); // 95
+```
+
+## 相关文档
+
+- [PoolAllocator 总览](pool-allocator.md) - 返回类总览