Zone matrix: partly, what is let through, hits; hc matrix aligned

A cell reads allow, block or partly (some new connections let through,
the rest not), with its exceptions counted by what they do (+3 -1), and
what they let through: services with the addresses they are limited to,
under the grid in hc matrix and in each cell on the Matrix page. A zone
to itself is marked: only traffic routed between its interfaces passes
the firewall. The details list each rule's hits. hc matrix pads the
grid by visible width: the colours' escape codes had thrown it out of
line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/rules.md

@@ -278,31 +278,60 @@ chain; from it: output; zone to zone: forward).
 
 ```
 $ hc matrix
-FROM \ TO  guest     lan       wan       firewall
-guest      block     block     block +1  block +3
-lan        block     block     allow     block +4
-wan        block +2  block +2  block +1  block +3
-firewall   allow     allow     allow     -
+FROM \ TO  guest         lan           wan         firewall
+guest      block *       block         partly +1   partly +4
+lan        block         block *       allow       partly +4
+wan        partly +1 -1  partly +1 -1  block -1 *  partly +3 -1
+firewall   allow         allow         allow       -
+
+Let through for part of the traffic:
+  guest → wan       http, https
+  guest → firewall  ICMPv6; ping; ssh from admins; dns
+  lan → firewall    ICMPv6; ping; ssh from admins; dns
+  wan → guest       1 port forward
+  wan → lan         1 port forward
+  wan → firewall    ICMPv6; DHCPv6; ssh from admins
+
+allow, block: every new connection; partly: some are let through, some not.
++N: rules that let part of the traffic through; -N: rules that block part of it. 'hc matrix FROM TO' lists them.
+*: a zone to itself: only traffic routed between its interfaces passes the firewall.
 ```
 
 Each cell walks that pair's rules in order, as nftables would, with the
 built-ins that act on new connections (ping from internal zones,
 ICMPv6, the DHCPv6 client, antispoofing, port forwards):
 
-* a rule that applies to the whole pair decides it ("allow", "block");
+* a rule that applies to the whole pair decides it;
 * a rule that applies to part of its traffic (some addresses, services,
-  times, rates, a quota) is an **exception** (+N), and the walk goes on;
+  times, rates, a quota) is an **exception**, and the walk goes on;
 * what's left falls to the deciding rule or the chain's policy.
 
+A cell reads **allow** or **block** when every new connection gets the
+same, and **partly** when exceptions let some through while the rest is
+blocked (or block some while the rest is allowed). **+N** counts the
+exceptions that let traffic through, **-N** those that block it. Under
+the grid (in the web UI, in each cell) is what the exceptions let
+through: their services, with the addresses they are limited to.
+
+A zone to itself (`*`, faded in the web UI) is mostly traffic that never
+reaches the firewall: within one interface's network it goes straight
+from host to host. Only what is routed between the zone's interfaces (or
+back out of the one it came in on) passes.
+
 `hc matrix guest wan` (or clicking the cell) lists the exceptions in
-order:
+order, with each rule's hits:
 
 ```
-guest → wan (the forward chain), new connections:
-  allowed  http, https   rule forward #14
-  blocked  the rest      forward policy
+guest → wan (the forward chain), new connections: partly allowed
+  VERDICT  WHAT         BY                HITS
+  allowed  http, https  rule forward #14  1520
+  blocked  the rest     forward policy    37
 ```
 
+The hits are the rule's packets since housecarld started, in all of its
+traffic: a rule without zones counts for every pair it covers. They are
+how you tell an exception that is used from one that isn't.
+
 A rule whose addresses all lie in networks directly connected to other
 zones is left out of a pair: traffic between those zones can't have them
 (`from wg_net` doesn't concern traffic coming in on the LAN). Routed