Pin formulahendry.acp-client 0.2.0 (Open VSX, MIT, sha256-verified) and point
acp.agents at `omp acp`. OMP already ships an ACP v1 server, so no custom
extension and no marketplace exception were needed.
Verified in the running IDE: status bar `ACP: Oh My Pi`, session/list returns
real prior OMP sessions for the open folder, and a full prompt turn streams
text plus tool-call and plan cards.
Credentials never move: OMP authenticates from ~/.omp via its `agent` auth
method and the extension is given no key.
