Bug: opencode adapter doesn't pass --model flag to opencode binary #80

What happened

The opencode adapter's launch() method builds args as ['run', prompt] but never includes --model. All opencode lanes in our open-weights coding trial silently used the default model instead of the specified one.

Expected

opencode run --model <model> <prompt>

Actual

opencode run <prompt> (model flag dropped)

Fix

// src/adapters/opencode.ts launch()
if (opts.model) {
  args.unshift('--model', opts.model);
}

Impact

All 3 opencode lanes in trial sweep g-8da467 produced no output because they launched with the wrong/default model.

Claude Code session is already working on the fix.