Memo 152 G-14: document deferred CLI bridge removals (next major)

[a6b8]

Two bridges are kept on purpose through the Memo 152 CLI split and should be removed with the next major: the dev prefix shim (src/index.mjs, isDevPrefix) and the dev allowlist add/remove deprecation no-op (src/commands/AllowlistCommand.mjs, Memo 150 UX). Add a 'Deferred removals (next major)' note to CHANGELOG so they are not forgotten or mistaken for live features. Doc-only, no code change.

Part of Memo 152 (PRD-025).