formatter subprocesses have no timeout and can hang the whole session

Describe the bug

packages/opencode/src/format/index.ts runs formatter subprocesses with no timeout or abort channel (appProcess.run is called without a timeout). handle.exitCode waits forever.

A formatter that hangs (e.g. mix format implicitly running a slow/failing mix compile, latexindent, or ktlint on a pathological file) blocks the whole session. Because formatting runs inside the edit/write/apply_patch tool call, the agent loop stalls and the model receives no error.

Suggested fix

Pass a timeout (e.g. matching webfetch's bounded-timeout pattern) to appProcess.run so a hung formatter fails the format step instead of hanging the session.

Environment

• opencode version: latest dev