test: add project name display tests

- Add comprehensive tests for getProjectDisplayName function
- Test various path structures including worktrees, nested projects, and edge cases
- Include regression tests for the reported bug cases
- Create separate utility file for better testability

Fixes session stats display where wrong fragments were shown
Related to: #348 (quota display), #103 (context display)

ui/src/components/analytics/project-name-utils.ts

@@ -0,0 +1,30 @@
+/**
+ * Project Name Utility Functions
+ *
+ * Utility functions for extracting meaningful project names from file paths
+ */
+
+/**
+ * Extracts the leaf folder name from a project path
+ *
+ * This function takes a full project path and returns just the leaf folder name,
+ * which represents the actual project name that the user would recognize.
+ *
+ * Examples:
+ * - '/home/user/projects/my-app' → 'my-app'
+ * - '/Users/joe/Developer/share-pi' → 'share-pi'
+ * - '/Users/joe/Developer/ExaDev/.../worktrees/2026-01-08' → '2026-01-08'
+ *
+ * @param path - The full project path
+ * @returns The leaf folder name (project name)
+ */
+export function getProjectDisplayName(path: string): string {
+  if (!path) return '';
+
+  // Remove leading/trailing slashes and split into segments
+  const cleanPath = path.replace(/^\/|\/$/g, '');
+  const segments = cleanPath.split('/').filter(segment => segment.length > 0);
+
+  // Return the last segment (leaf folder name)
+  return segments[segments.length - 1] || '';
+}

ui/src/components/analytics/session-stats-card.tsx

@@ -13,6 +13,7 @@ import type { PaginatedSessions } from '@/hooks/use-usage';
 import { cn } from '@/lib/utils';
 import { formatDistanceToNow } from 'date-fns';
 import { usePrivacy, PRIVACY_BLUR_CLASS } from '@/contexts/privacy-context';
+import { getProjectDisplayName } from './project-name-utils';
 
 interface SessionStatsCardProps {
   data: PaginatedSessions | undefined;
@@ -152,16 +153,6 @@ export function SessionStatsCard({ data, isLoading, className }: SessionStatsCar
   );
 }
 
-function getProjectDisplayName(path: string): string {
-  if (!path) return '';
-
-  // Remove leading/trailing slashes and split into segments
-  const cleanPath = path.replace(/^\/|\/$/g, '');
-  const segments = cleanPath.split('/').filter(segment => segment.length > 0);
-
-  // Return the last segment (leaf folder name)
-  return segments[segments.length - 1] || '';
-}
 
 function formatCompact(num: number): string {
   if (num >= 1_000_000_000) return `${(num / 1_000_000_000).toFixed(1)}B`;