fix: replace leftover amber color on 'Start reading' file pill

ec-entry-hint code had rgba(237,186,154,...) from an old warm palette.
Updated to blueprint accent rgba(91,143,249,...) to match the rest of the UI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/index.css

@@ -3709,8 +3709,8 @@ textarea:focus-visible {
 }
 
 .ec-entry-hint code {
-  background: rgba(237,186,154,0.12);
-  border: 1px solid rgba(237,186,154,0.25);
+  background: rgba(91,143,249,0.12);
+  border: 1px solid rgba(91,143,249,0.28);
   color: var(--accent-soft);
   padding: 1px 6px;
   border-radius: 4px;