Update streaming handling and improve model validation

Add MAX_STREAM_CHUNKS constant and update message handling to mark streaming as complete even without tool results.
Improve model name validation to support colons and add comprehensive test suite. Refactor VaultIndexer to simplify
constructor and remove unused methods. Fix path normalization in tool executor and remove unused safeWriteFile export.
Update error handling to remove redundant console suppressions.

tests/utils.test.ts

@@ -58,7 +58,7 @@ describe('Validation Functions', () => {
       const invalidModel = validateModelName('llama@2');
       expect(invalidModel.valid).toBe(false);
       expect(invalidModel.error).toContain(
-        'only contain letters, numbers, dots, dashes, and underscores'
+        'only contain letters, numbers, dots, dashes, underscores, and colons'
       );
     });