Fix Diagnostic Snippets with Tabs

[rcosta358]

This PR improves the accuracy of diagnostic code snippets by correctly handling tab characters when displaying error markers. This ensures that caret markers (^) align visually with the intended columns, even when the source code contain tabs instead of spaces.

Before

Refinement Error: #x_1 == -1 is not a subtype of #x_1 > 0
10 |    void test() {
11 |            @Refinement("_ > 0")
12 |            int x = -1;
   |       ^^^^^^^
13 |    }
14 | 

After

Refinement Error: #x_1 == -1 is not a subtype of #x_1 > 0
10 |     void test() {
11 |         @Refinement("_ > 0")
12 |         int x = -1;
   |             ^^^^^^^
13 |     }
14 |