- Added first-fit free-list allocator with block splitting and coalescing.
Provides kmalloc(), kfree(), and kcalloc() for kernel-space dynamic memory.
- Each block carries an inline header with a magic value (0xCAFEBABE) for
heap corruption detection, plus double-free checking.
- Memory is obtained from the paging subsystem in 4 KiB page increments.
All allocations are 8-byte aligned with a 16-byte minimum block size.
- Created freestanding string.c with memset, memcpy, memmove, memcmp,
strlen, strcmp, strncmp, strcpy, strncpy — replacing the unavailable
libc implementations.
- Added documentation in docs/kmalloc.md.
Tested: kmalloc(64) returns 0xD0001010 (in kernel heap) and kfree succeeds.
Works with both 4 MiB and 128 MiB RAM.
