docs(tag): clarify TagExpand's runtime validation behavior

Signed-off-by: Johan Lindh <johan@linkdata.se>

Author: linkdata

lib/tag/doc.go

@@ -1,8 +1,6 @@
 // Package tag expands JaWS tag values into comparable keys that identify
 // elements during dirtying, broadcasts and event routing.
 //
-// The runtime tag-comparability check in [TagExpand] is gated on
-// deadlock.Debug, so it (and full statement coverage of this package) is only
-// exercised when the tests run with the -race flag or -tags debug. Always test
-// with -race.
+// [TagExpand] rejects values that are not usable as hashable tag keys, including
+// values whose static type is comparable but whose runtime contents are not.
 package tag