docs: T8887: address review feedback and pre-existing lint debtdocs/t8887-phase1-batch1

- router-advert: reword base-interface description — the base interface
  provides the network portion of the advertised RA prefix (radvd
  Base6Interface), not the host bits; note the DHCPv6-PD use case
- route-map, ipsec_general: wrap five pre-existing overlong lines so the
  doc linter (which scans whole modified files) passes on touched files

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1 files changed, 4 insertions, 3 deletions

diff --git a/docs/configuration/service/router-advert.md b/docs/configuration/service/router-advert.md
index 9a70067e..7f0ba895 100644
--- a/docs/configuration/service/router-advert.md
+++ b/docs/configuration/service/router-advert.md
@@ -62,9 +62,10 @@ from DHCPv6-PD.
 ```{cfgcmd} set service router-advert interface \<interface\> prefix \<prefix\> base-interface \<interface\>
 
 The advertised prefix is combined with the IPv6 address of the specified
-interface (for example, a WAN interface) to derive the advertised prefix's
-host bits. This option is only allowed together with the wildcard prefix
-`::/64`.
+interface (for example, a WAN interface) so that the network portion of
+the RA prefix follows that interface's current IPv6 address. This option
+is only allowed together with the wildcard prefix `::/64`, and is the
+typical way to re-advertise a DHCPv6-PD-assigned prefix.
 ```
 
 ```{eval-rst}