Add changelog entry for pre-compare code review improvements

Documents the implementation fixes and test coverage improvements
applied during code review of the pre-compare feature.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mavam

changelog/unreleased/improve-pre-compare-feature-implementation.md

@@ -0,0 +1,11 @@
+---
+title: Improve pre-compare feature implementation
+type: change
+authors:
+  - mavam
+  - claude
+pr: 10
+created: 2026-01-30T21:42:17.238928Z
+---
+
+Fixed and improved the `pre-compare` feature based on code review feedback. The `apply_pre_compare` function is now a public API so all runners apply transforms consistently. Fixed a bug in ShellRunner where transforms weren't applied when comparing empty output against a baseline. Improved variable naming and documentation throughout the runners, and added comprehensive test coverage including integration tests and parameterized unit tests to ensure consistent behavior across all test runners.