Fix color regressions, add priority color (#37417)

- fix markup attention block regressions on 2 colors
- added new color "priority" color for important severity in markup
- all message-box style, and error form elements use monochrome text
- tweaked and improved action logs colors

Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

web_src/js/components/PullRequestMergeForm.vue

@@ -230,7 +230,7 @@ function clearMergeMessage() {
   bottom: -1px;
   position: absolute;
   align-items: center;
-  color: var(--color-info-text);
+  color: var(--color-text);
   background-color: var(--color-info-bg);
   border: 1px solid var(--color-info-border);
   border-left: none;
@@ -238,7 +238,7 @@ function clearMergeMessage() {
 }
 
 .auto-merge-small:hover {
-  color: var(--color-info-text);
+  color: var(--color-text);
   background-color: var(--color-info-bg);
   border: 1px solid var(--color-info-border);
 }