contact messages: trigger hover follows the navbar tab idiom

The filled button now hovers like nitro's accent nav tab: text --ink (falling back to --bg on themes without it) switching to the bright --tab-hover with the same text-shadow glow, instead of the invented fill shift.

frontend/src/assets/pagerite.css

@@ -881,16 +881,16 @@ article {
 /* {contact: Label} directive: the button opening the visitor contact
    panel (docs/messages.md). A standalone accent button in the article
    flow; .has-unread (set by contact-main) marks a new admin reply.
-   Filled with the accent (text in --bg, the pairing the accent is
-   designed to contrast with); hover nudges the fill toward the page
-   text color — a subtle shift that works in either color scheme — and
-   keyboard focus gets an outline instead of a restyle. */
+   Filled with the accent and hovered like the accent-filled navbar tab:
+   text in --ink (nitro; --bg elsewhere), hover switches to the bright
+   --tab-hover with the same glow (text-shadow, which fades dimmer, so
+   the color stays bright). */
 .contact-trigger {
   position: relative;
   margin: 0.3em 0.1em;
   padding: 0.35em 1.1em;
   font: inherit;
-  color: var(--bg);
+  color: var(--ink, var(--bg));
   background: var(--accent);
   border: 1px solid var(--accent);
   border-radius: 1.2em;
@@ -898,8 +898,8 @@ article {
 }
 
 .contact-trigger:hover {
-  background: color-mix(in srgb, var(--accent) 85%, var(--text));
-  border-color: color-mix(in srgb, var(--accent) 85%, var(--text));
+  color: var(--tab-hover, var(--bg));
+  text-shadow: 0 0 0.1em;
 }
 
 .contact-trigger:focus-visible {