UI/UX sweep: CLI #183

--json is the contract and the human output is not, so nobody has designed the human output. email list prints tab-separated columns because keys list does. Decide the rules once, write them on the wiki's Users page, then apply them noun by noun:

• column layout and alignment for list commands
• what goes to stdout and what to stderr
• how a refusal reads: exit 4 messages should say what to do instead
• how usage errors read, and whether every command names its usage
• consistency of verbs across nouns (list, show, create, remove, edit)

Output: the rules on the wiki, then one MR per noun.