Pattern 6: Large 1D array (2000 elements) — exercises zero-alloc
_check_wrapper_mutation! with pointer-first check.
Pattern 7: Large N-D array (4×21×21) — exercises wrapper mutation
check on multi-dimensional arrays.

These were present in fix/borrow_registry but missing from the clean
reimplementation. Renumber existing others patterns to 8 and 9.

… types

sizeof(T) crashes on Julia 1.10 when T is a non-isbits type like
Vector{Float64} (Array is an opaque C-backed type without definite size).
Use inline isbitstype check consistent with _safe_elsize in debug.jl,
avoiding cross-file dependency on include order.

The fast path in _check_others_pointer_overlap was checking ALL entries
in _others_ptr_bounds, including bounds from outer scopes. This caused
false positives: returning an array acquired in an outer scope from an
inner scope would incorrectly trigger PoolRuntimeEscapeError.

Fix: use _others_ptr_bounds_checkpoints[end] as scope boundary, only
checking bounds recorded after the current scope's checkpoint — matching
the _scope_boundary pattern used by _check_tp_pointer_overlap for
fixed-slot types.

- others type: outer-scope array returned from inner scope is NOT an escape
- others type: inner-scope array returned from inner scope IS an escape
- fixed slot: same tests for parity verification
- Pattern 10: nested others + cross-scope validate is zero-alloc (S=1)