The SSE proxy was buffering the entire response body with a 30s read
timeout, causing 504s on the OpenCode /global/event stream. Add a
streaming path that detects SSE requests (by Accept header or /event
path) and returns a StreamingResponse with no read timeout.
Also fix the make try target to poll the health endpoint for Docker
readiness and wait for the container to reach running status before
opening the browser.
The try and session targets were hitting /sessions directly instead of
/api/sessions (Caddy strips the /api prefix before proxying). Also, try
now depends on up and waits for health check before creating a session.
