Fix audit findings in mv, touch, rmdir, mktemp

[kelp]

Summary

• mv: Hardlink same-file move (same inode, different paths) now unlinks the source and exits 0 instead of erroring
• touch: -h/--no-dereference implies -c (no create) so nonexistent files are not created when the intent is to operate on a symlink
• rmdir: Verbose message prints before the removal attempt so --ignore-fail-on-non-empty no longer suppresses -v output
• mktemp: Templates with implicit suffixes (e.g., myapp.XXXXXXtxt, test.XXXXXX.log) are now accepted by finding the last run of 3+ consecutive X's

Test plan

• just it-util mv -- 110 passed, 1 skipped, 0 failed
• just it-util touch -- 120 passed, 0 failed
• just it-util rmdir -- 46 passed, 0 failed
• just it-util mktemp -- implicit suffix tests pass (5 pre-existing failures in bare-template/cwd and -t/slash tests are unrelated)
• zig build test -- all unit tests pass