feat: improve Debug output for index types (#92)

Changes the Debug output format for types created with `define_nonmax_u32_index_type!` from just the raw number (e.g., `42`) to include the type name (e.g., `ScopeId(42)`).

This makes debug output and error messages much clearer, especially when displaying multiple different index types together. For example, in semantic analysis snapshots, scope and symbol IDs are now clearly distinguished:

Before:
```
Scope children mismatch:
after transform: 0: [1]
rebuilt        : 0: [1, 2, 4]
```

After:
```
Scope children mismatch:
after transform: ScopeId(0): [ScopeId(1)]
rebuilt        : ScopeId(0): [ScopeId(1), ScopeId(2), ScopeId(4)]
```

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

Co-authored-by: Claude <[email protected]>

Author: Boshen

src/macros.rs

@@ -328,7 +328,7 @@ macro_rules! define_nonmax_u32_index_type {
 
         impl core::fmt::Debug for $type {
             fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-                write!(f, "{}", self.index())
+                write!(f, "{}({})", stringify!($type), self.index())
             }
         }
 

tests/test.rs

@@ -611,9 +611,9 @@ fn test_nonmax_with_attrs() {
     // Test that custom attributes work with define_nonmax_u32_index_type!
     let idx = IdxNonMaxWithAttrs::new(42);
 
-    // Verify Debug derive works
+    // Verify Debug impl works
     let debug_str = format!("{:?}", idx);
-    assert_eq!(debug_str, "42");
+    assert_eq!(debug_str, "IdxNonMaxWithAttrs(42)");
 
     // Verify all standard functionality works
     assert_eq!(idx.index(), 42);