tests: expand host unit tests from 47 to 101 checks

tests: expand host unit tests from 47 to 101 checks

test_utils.c (28→63):
- tar_parse_octal: zero, simple, large, empty, null-term, non-octal skip
- path_is_mountpoint_prefix: root, exact, child, no-match, partial, empty
- normalize_mountpoint: root, simple, trailing-slash, empty, null, normalized
- vfs_check_permission: root, owner/group/other read/write, mode-0, 0644
- elf32_validate: valid ET_EXEC/ET_DYN, bad magic/class/type/machine,
  no phnum, truncated, null

test_security.c (19→38):
- Signal mask: valid excludes KILL/STOP, includes USR1,
  pending&blocked, deliverable/blocked, KILL/STOP always deliverable
- chmod symbolic: u+x, go-w, a+x, a=rw, u+s, g+s, +t, o-x,
  u=rw,go=r, no-change

gdb_checks.py (6→10):
- Process table PID 1 state check
- Scheduler active runqueue bitmap
- Mount table count
- Frame 0 refcount

Test results: 63/63 + 38/38 + 111/111 = 212 host PASS