fix: improve inline code rendering in signal details (#1579)

### Problem
Inline code (backtick content) in signal card details is barely visible. The `Code` component uses `variant="ghost"` which has no background, and the parent container applies `color: var(--gray-11)` which makes inline code blend into surrounding text.

### Fix
Added explicit CSS rules for `code` elements in the signal card body:
- `bg-gray-4` — subtle background to distinguish code from text
- `rounded` — rounded corners
- `px-1 py-0.5` — padding for visual separation
- `font-mono` — explicit monospace font

This makes inline code clearly distinguishable from surrounding text while maintaining the compact signal card layout.

Fixes #1567

Author: reverb256

apps/code/src/renderer/features/inbox/components/detail/SignalCard.tsx

@@ -252,7 +252,12 @@ function SignalCardHeader({
 function CollapsibleBody({ body }: { body: string }) {
   const [expanded, setExpanded] = useState(false);
   const isLong = body.length > COLLAPSE_THRESHOLD;
-  const displayBody = isLong && !expanded ? truncateBody(body) : body;
+  // Preprocess content to handle escaped backticks and ensure proper markdown parsing
+  const processedBody = body
+    .replace(/\\`/g, "`") // Unescape escaped backticks
+    .replace(/`([^`]+)`/g, "`$1`"); // Ensure proper backtick formatting
+  const displayBody =
+    isLong && !expanded ? truncateBody(processedBody) : processedBody;
 
   return (
     <Box>