4460475fb0
Folds a dead key (' ` ^ " ~) plus the following letter into one Latin-9
Key::Char, with the roadmap's `'`+c -> ç case and `'`+space -> literal
apostrophe. Pure and host-tested (12 new tests, 25 total pass).
Not wired into the live decode path yet: it emits non-ASCII and the
editor buffer still assumes byte==char, so wiring waits on the v0.2
UTF-8-correct buffer.