Release 2.6.0

Add write-protection, safety fixes, bump v2.6.0

Multiple safety and correctness changes: bump KPM_VERSION to 2.6.0; include linux/sched; resolve and use __arch_clear_user; sanitize user pointers by clearing the top byte; change pgt_pgtable_to_tkpa to accept an is_write flag and reject writes to read-only descriptors/tables; add a stack bounce buffer (HMKPM_BOUNCE_SIZE) and copy choreography for pgt_rw_mm to avoid in-lock user copies; disallow writes in lockless mode; switch to per-page mmap locking and untag user addresses in single/batch handlers.