fix: resolve UBSAN and ASAN reported undefined behavior and bugs

[Akilan-Sivakumar]

• Fixed signed left-shift undefined behavior reported by UBSAN.
• Replaced unsafe function-pointer casts in the HIGH_BIT_DEPTH primitive aliasing with safe trampolines that only reinterpret data pointers.
• Added guards for out-of-bounds access, division-by-zero, and uninitialized/stale reads flagged by ASAN.
• Fixed a TestBench segfault at high bit depth caused by the new alias trampolines.