Two more value-observable families ported additively (the .c sources
keep running in $(TESTS); de-dup deferred to fold 6).
932_str_elem_cap -> str_elem_cap_test: a str-element N_INDEX value
read must load the full 24B {ptr,len,cap}, not {ptr,len} (F2); each
shape poisons cap != len so a 2-word read fails the .cap assert.
Template for the 933-939 cap family.
957_size_type -> size_type_test: `size` binds in type position and
coexists with the size(T) operator (#85); a green row is the bind
proof.