[docs] Clarify maintainer responsibility for direct AI changes

Address review feedback on the AI conduct policy lead-in.

Keep the expectation that a human contributor owns AI-assisted
submissions before review, while clarifying that if a maintainer
accepts a machine-originated change directly, that maintainer takes
responsibility for it.

Assisted-by: Codex

CODE_OF_AI_CONDUCT.md

diff --git a/CODE_OF_AI_CONDUCT.md b/CODE_OF_AI_CONDUCT.md
index 3d6f021..51975c6 100644
--- a/CODE_OF_AI_CONDUCT.md
+++ b/CODE_OF_AI_CONDUCT.md
@@ -1,7 +1,9 @@
 # Code of AI Conduct
 
-This project accepts AI-assisted contributions, but contributors remain fully
-responsible for the changes they submit.
+This project accepts AI-assisted contributions. Before review, a human
+contributor is expected to take full responsibility for the changes they
+submit. If a maintainer chooses to accept a machine-originated change directly,
+that maintainer takes the same responsibility for it.
 
 ## Requirements