sync: vendor mattpocock/skills @49dd158 (v1.3.1) with sync tooling

upstream/skills/engineering/pr/CREDITS.md

@@ -0,0 +1,3 @@
+# Credits
+
+The **Summary** section's menu of visuals (pseudocode, call trees, component trees, file trees, Mermaid, diffs) and its placement guidance come from [Dex Horthy](https://github.com/dexhorthy)'s [`show-me`](https://github.com/humanlayer/humanlayer) skill, reproduced almost word for word and aimed at a diff instead of a live conversation. `pr` does not depend on `show-me` as a skill (it isn't part of this repo, and a hard dependency would break standalone installs), so the content is copied in rather than pointed at; this file is the attribution a dependency would otherwise have carried.