Update ApplicationFinderTests to use modern Swift Testing patterns

- Replace #expect(throws:) with more expressive error validation pattern
- Use #expect { } throws: { } for better error type checking
- Improve error handling in nonExistentAppThrowsError test

🤖 Generated with [Claude Code](https://claude.ai/code)

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

peekaboo-cli/Tests/peekabooTests/ApplicationFinderTests.swift

@@ -386,8 +386,14 @@ struct ApplicationFinderEdgeCaseTests {
     @Test("Non-existent app throws error", .tags(.fast))
     func nonExistentAppThrowsError() {
         // Test with a completely non-existent app name
-        #expect(throws: ApplicationError.notFound("XyzNonExistentApp123")) {
+        #expect {
             _ = try ApplicationFinder.findApplication(identifier: "XyzNonExistentApp123")
+        } throws: { error in
+            guard let appError = error as? ApplicationError,
+                  case let .notFound(identifier) = appError else {
+                return false
+            }
+            return identifier == "XyzNonExistentApp123"
         }
     }