Re-land OpenCode CLI support after rollback #170
Description
We reset main back to the last known-good commit 71228ca (fix: restore audit baseline branch build) to get out of the visible-first transport regression.
That reset also dropped the finished OpenCode CLI work from commit a7bf096bf3d8bf57060bace58dbfd2b0a0e056a8 (feat: add OpenCode CLI support). This should not be reimplemented from scratch; the work already exists and just needs to be merged back cleanly on top of the post-rollback base.
Concrete references:
- commit: a7bf096bf3d8bf57060bace58dbfd2b0a0e056a8
- branch: codex/opencode-cli-agent
- worktree: /home/user/code/freshell/.worktrees/opencode-cli-agent
Requested outcome:
- re-land the finished OpenCode CLI support on top of main
- keep it separate from the visible-first / transport stack
- verify tests still pass after re-landing