doc: am: fill out hook discussion

Document `--verify` and rephrase the `--[no-]verify` section to lead with the default, in imperative mood.[1] Historically it makes sense that only the negated forms are documented; they are all run by default and thus you only need to use hook options if you want to turn some of them off. But, beyond just desiring uniform documentation,[2] it’s very much possible to have, say, a Git alias with `--no-verify` that you might sometimes want to turn back on with the *positive* form. Also mention the options in the “Hooks” section and mention that `post-applypatch` cannot be skipped. † 1: See e.g. acffc5e9 (doc: convert git-remote to synopsis style, 2025-12-20) † 2: https://lore.kernel.org/git/xmqqcyct1mtq.fsf@gitster.g/ Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name> Signed-off-by: Junio C Hamano <gitster@pobox.com>