test(opencode): align unknown finish coverage

[opencode-agent]

Summary

• update non-interactive CLI expectations for unknown-finish continuation
• verify partial text remains visible before the recovered response
• verify JSON event order includes the unknown step and successful continuation

Why

The prompt loop now continues after every unknown finish. Two CLI tests still asserted the previous behavior, where the process stopped immediately after persisting the unknown step. These expectations now exercise the intended continuation and recovery behavior instead.

Testing

• bun test test/cli/run/run-process.test.ts -t "unknown stream finish" (2 pass)
• git diff --check

Requested by: @thdxr (dax via Slack)