Fix missing diagnostic and text highlights after blocks (#19920)

Release Notes:

- Fixed an issue where diagnostic underlines and certain text highlights
were not rendered correctly below block decorations such as the inline
assistant prompt.

Co-authored-by: Antonio <antonio@zed.dev>
Co-authored-by: Richard <richard@zed.dev>

crates/language/src/buffer.rs

@@ -4103,6 +4103,10 @@ impl<'a> BufferChunks<'a> {
                 diagnostic_endpoints
                     .sort_unstable_by_key(|endpoint| (endpoint.offset, !endpoint.is_start));
                 *diagnostics = diagnostic_endpoints.into_iter().peekable();
+                self.hint_depth = 0;
+                self.error_depth = 0;
+                self.warning_depth = 0;
+                self.information_depth = 0;
             }
         }
     }