`ssh <forge> tell <words>` tells the crew in one line from any shell, and prints where it went #6110

Steering is one thought. Today an exec on the forge's SSH is git or nothing, and telling the crew from a shell means opening the whole terminal UI.

Done when:

• [ ] An exec of tell <words> on a non-app login, with a key that belongs to an account, calls the same tell action the web composer and the TUI use (src/actions/tell.ts), with from null. It prints the told line (toldWords) and the full URL of where it went, then exits 0.
• [ ] An unknown key prints the account-needed refusal to stderr, records nothing and exits 1. Empty words print SAY_SOMETHING_WORDS. Words over the limit print TOO_LONG_WORDS. An unverified account prints UNVERIFIED_WORDS. None of these records anything.
• [ ] The words are taken as given, with no shell expansion and no eval. Control characters are refused at the boundary.
• [ ] A test drives forgeSshSession with a fake exec session for each case above and reads the tell back from the database.
• [ ] The README's terminal section names the command.

Files: src/tui/ssh.ts (exec dispatch), test/ssh-tell.test.ts, README.md. Risk: src/tui/ssh.ts is shared with the pulls issue; rebase on whichever lands first.