feat(root): add KernelSU timing side-channel detection

[ZnDong]

Implement kernel-level syscall hook detection for KernelSU by comparing faccessat (hooked by KSU) vs fchownat (not hooked) execution timing.

Reference: https://bbs.kanxue.com/thread-288928.htm

Detection algorithm:

• Bind thread to big core for stable measurements
• Collect 10000 timing samples for both faccessat and fchownat
• Use hardware counter (CNTVCT_EL0) on ARM64 for nanosecond precision
• Sort both arrays to reduce noise and outliers
• Compare element-by-element: count cases where faccessat > fchownat + 1
• If anomaly rate exceeds 70% (7000/10000), KernelSU hook detected

Key design decisions:

• Both syscalls use dirfd=-1 (invalid fd) to ensure symmetric kernel failure paths; using AT_FDCWD would cause faccessat to enter deeper kernel code (path resolution + page fault) leading to false positives
• faccessat chosen because it is in KSU hook list, is simple, fast, and failure has no side effects

Files changed:

• syscall_wrapper.h: core detection functions (counter, CPU binding, sample collection, comparison, threshold check)
• native-lib.cpp: JNI bindings for ksuSideChannelCheck/Detected
• NativeDetector.java: native method declarations
• SideChannelDetector.java: Java detection item integration