fix: shell/command bugs, new utilities, procfs race condition

fix: shell/command bugs, new utilities, procfs race condition

Shell fixes:
- Fix DELETE key showing ~ (handle \x1b[3~ escape sequence + Home/End)
- Fix builtin redirections (echo > file now works via saved fd restore)
- Fix initrd readdir (root cause of ls /bin empty + tab completion broken)

Command fixes:
- Fix cut -dX/-fN combined argument parsing (POSIX style)
- Fix ps showing ? for PIDs: add cmdline[128] to process struct, populate in execve + init
- Fix procfs race condition: use sched_lock for process list traversal
- Make sched_lock non-static for procfs access

New commands (22 total):
- Previous session: mount, umount, env, kill, sleep, clear, ps, df, free, tee, basename, dirname, rmdir
- This session: grep, id, uname, dmesg, printenv, tr, dd, pwd, stat

Arch contamination note: vdso.c includes arch/x86/kernel_va_map.h directly (acceptable for now, only x86 target)

Tests: 89/89 smoke, cppcheck clean