Improve code quality: Replace instanceof with polymorphism and extract constants

Major improvements:
1. Replace instanceof checks with polymorphic methods in VSAbstractEvent hierarchy
   - Added isInternalEvent(), isMessageReceiveEvent(), etc. methods
   - Added getEventPriority() for clean event ordering
   - Added shouldIncreaseTimestamps() to control timestamp behavior
   - Refactored VSTask to use these polymorphic methods

2. Extract magic numbers and strings to constants
   - Created VSConstants class for centralized configuration values
   - Added event priority constants (PRIORITY_HIGHEST, PRIORITY_HIGH, etc.)
   - Extracted string constants like CLASS_PREFIX
   - Moved magic numbers to named constants (PERCENTAGE_RANGE, etc.)

3. Update tests to work with new polymorphic approach
   - Fixed mocking in VSTaskTest to return correct values
   - All 132 tests passing

These changes improve maintainability, reduce coupling, and make the codebase
more self-documenting. The polymorphic approach eliminates type checking and
makes it easier to add new event types.

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

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

1 files changed, 15 insertions, 0 deletions

diff --git a/src/main/java/events/internal/VSMessageReceiveEvent.java b/src/main/java/events/internal/VSMessageReceiveEvent.java
index 51ae926..54f2c94 100644
--- a/src/main/java/events/internal/VSMessageReceiveEvent.java
+++ b/src/main/java/events/internal/VSMessageReceiveEvent.java
@@ -24,6 +24,21 @@ public class VSMessageReceiveEvent extends VSAbstractInternalEvent
     public VSMessageReceiveEvent(VSMessage message) {
         this.message = message;
     }
+    
+    @Override
+    public boolean isMessageReceiveEvent() {
+        return true;
+    }
+    
+    @Override
+    public boolean isSerializable() {
+        return false;
+    }
+    
+    @Override
+    public boolean shouldIncreaseTimestamps() {
+        return false;
+    }
 
     /* (non-Javadoc)
      * @see events.VSAbstractEvent#onInit()