Record skill consolidation PR

docs/implementation.md

@@ -131,3 +131,5 @@ without content changes; root policy links and this record now use that location
 The old root `skills/` directory is removed. Validation compares moved content
 byte-for-byte, checks all four skill paths and updated UX links, and runs
 `git diff --check`. No runtime tests are needed for this move.
+
+Delivery: [PR #17](https://git.sendico.io/tech/sxchnge/pulls/17), branch `skills-16`.