refactor: simplify tool call display and path handling

- Remove displayName from tool calls, use name directly with icon
- Add medium font weight for tool call badges
- Strip workspace root from file paths at parsing level using Zod schema
- Add accentBorder to tool call badges and git diff file blocks
- Fix user message alignment and vertical spacing
- Deduplicate stripCwdPrefix into tool-call-parsers.ts

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/app/src/components/git-diff-pane.tsx

@@ -315,7 +315,7 @@ const styles = StyleSheet.create((theme) => ({
     overflow: "hidden",
     backgroundColor: theme.colors.muted,
     borderWidth: theme.borderWidth[1],
-    borderColor: theme.colors.border,
+    borderColor: theme.colors.accentBorder,
     marginBottom: theme.spacing[2],
   },
   fileHeader: {