chore(claude): Add standalone update-changelogs skill

Author: rekmarks

.claude/skills/update-changelogs/SKILL.md

@@ -0,0 +1,10 @@
+---
+name: update-changelogs
+description: Updates changelogs for all packages with consumer-facing changes.
+---
+
+When asked to update changelogs, follow these steps:
+
+1. Read the instructions in [`docs/contributing/updating-changelogs.md`](../../../docs/contributing/updating-changelogs.md) and follow them to the letter.
+2. Commit the changes to the current branch with the commit message "docs: Update changelogs" before creating the PR.
+3. Return the commit hash and the commit message.