Bug: opencode adapter wrapper exits immediately while opencode process continues running #86

What happened

When launching opencode via agentctl, the wrapper process exits almost immediately (0s duration) even though the underlying opencode process is still running. This makes agentctl list unable to track the session — it shows as stopped while the real work continues.

Evidence

$ agentctl launch opencode --model 'openrouter/qwen/qwen3.5-35b-a3b' --cwd ~/code/mono-v5-8460-qwen35 -p '...'
Launched session pending-95449 (PID: 95449)

# Immediately after:
$ agentctl list -a | grep 95449
# Nothing — already gone

# But the actual opencode process was still running:
$ ps aux | grep opencode | grep qwen
ms  94142  opencode run --model openrouter/qwen/qwen3.5-35b-a3b ...

Workaround

Launch opencode directly with nohup:

nohup opencode run --model '...' 'prompt' > /tmp/log.log 2>&1 &

This works but bypasses agentctl's session tracking entirely.

Root cause guess

The adapter spawns opencode detached but the wrapper process doesn't wait long enough to capture the session ID or confirm the child is running. The child outlives the wrapper.

Impact

• Can't use agentctl list to monitor opencode sessions
• Can't use agentctl logs to read output
• Matrix sweep launches appear to fail when they're actually running
• Session metadata never gets written so recovery is impossible