pw: make manual page more friendly for uid/gid search

pw.8 structure is quite different from usual manual page, especially in
describing -o option usage.  Specifically, these paragraphs do not
contain "uid/gid" terms, and have "user id"/"group id" instead,
making searching for "override duplicate safety belt" difficult.
Try to simplify such searches.

Also, clarify uid/gid space between 100 and 1000 as "somewhat special",
as it actually is.

Discussed on:   russian telegram FreeBSD group
Reviewed by:	eugen, novel
MFC after:      1 week

usr.sbin/pw/pw.8

@@ -22,7 +22,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 19, 2025
+.Dd February 11, 2026
 .Dt PW 8
 .Os
 .Sh NAME
@@ -572,8 +572,8 @@ It is possible to use
 to create a new account that duplicates an existing user id.
 While this is normally considered an error and will be rejected, the
 .Fl o
-option overrides the check for duplicates and allows the duplication of
-the user id.
+option overrides the check for uniqueness and allows the duplication of
+the uid.
 This may be useful if you allow the same user to login under
 different contexts (different group allocations, different home
 directory, different shell) while providing basically the same
@@ -686,6 +686,9 @@ In general,
 user and group ids less than 100 are reserved for use by the system,
 and numbers greater than 32000 may also be reserved for special purposes
 .Pq used by some system daemons .
+Also, uids and gids between 100 and 999 are commonly used by pseudo-users
+assotiated with third-party programs, and generally should be avoided for
+assigning for normal users.
 .It Fl w Ar passmethod
 The
 .Fl w
@@ -886,7 +889,7 @@ also has a
 option that allows allocation of an existing group id to a new group.
 The default action is to reject an attempt to add a group,
 and this option overrides the check for duplicate group ids.
-There is rarely any need to duplicate a group id.
+There is rarely any need to duplicate a gid.
 .Pp
 The
 .Cm groupmod