Improve commit detection in CodeDiff validator

[academo]

Problem

The CodeDiff validator currently uses heuristics (with Gemini CLI assistance) to detect the commits between plugin versions for diff analysis. This detection is failing often, leading to incorrect or missing diffs.

The key challenge is accurately identifying:

• The commit representing the last published version
• The commit representing the current version being validated

Proposed Solution

Investigate and improve the commit detection logic to more reliably find the correct commits between versions.

Tasks

• Analyze current commit detection implementation and identify failure cases
• Improve heuristics for finding version commits
• Add tests for commit detection edge cases