fix: resolve final test compilation issues

- Add missing Foundation import in ClaudeSessionTrackerTests for TimeInterval and UUID types
- Remove unnecessary nil check for non-optional TokenColor in TokenDebuggerTests
- All tests now compile successfully without errors or warnings

Author: steipete

VibeMeterTests/Services/ClaudeSessionTrackerTests.swift

@@ -1,3 +1,4 @@
+import Foundation
 import Testing
 @testable import VibeMeter
 

VibeMeterTests/TokenDebuggerTests.swift

@@ -36,9 +36,8 @@ struct TokenDebuggerTests {
 
         #expect(!viz.segments.isEmpty)
 
-        // Verify all segments have valid colors
+        // Verify all segments have valid tokens
         for segment in viz.segments {
-            #expect(segment.color != nil)
             #expect(segment.token >= 0)
         }
     }