Add deterministic QueryPerformanceCounter/Frequency mocks

Implemented Windows high-resolution timing mocks for deterministic simulation:

**mock_QueryPerformanceCounter:**
- Returns deterministic counter based on simulated_time
- Uses fixed 10 MHz frequency (10,000,000 counts/second)
- Calculation: count = (tv_sec * freq) + (tv_nsec * freq / 1e9)
- Validates NULL pointer with ERROR_INVALID_PARAMETER
- Provides consistent, reproducible timing across test runs

**mock_QueryPerformanceFrequency:**
- Returns fixed frequency of 10 MHz (10,000,000 Hz)
- Common frequency on modern Windows systems
- Ensures deterministic behavior (no variation between runs)
- Validates NULL pointer with ERROR_INVALID_PARAMETER

**Integration:**
- Added function declarations to system.h
- Macros already existed (sys_QueryPerformanceCounter/Frequency)
- Complements existing mock_clock_gettime on Linux
- Both platforms now have deterministic high-resolution timing

This ensures Windows code using QueryPerformanceCounter for timing,
benchmarking, or rate limiting behaves deterministically in tests.
The fixed 10 MHz frequency provides nanosecond-level precision
(100ns per tick) suitable for most timing needs.

src/system.h

@@ -61,6 +61,8 @@ BOOL   mock_FlushFileBuffers(HANDLE handle);
 BOOL   mock_ReadFile(HANDLE handle, char *dst, DWORD len, DWORD *num, OVERLAPPED *ov);
 BOOL   mock_WriteFile(HANDLE handle, char *src, DWORD len, DWORD *num, OVERLAPPED *ov);
 BOOL   mock_GetFileSizeEx(HANDLE handle, LARGE_INTEGER *buf);
+BOOL   mock_QueryPerformanceCounter(LARGE_INTEGER *lpPerformanceCount);
+BOOL   mock_QueryPerformanceFrequency(LARGE_INTEGER *lpFrequency);
 char*  mock__fullpath(char *path, char *dst, int cap);
 int    mock__mkdir(char *path);
 #else