Chat shows 'working...' indefinitely after opencode CLI already finished responding

Description

After updating to the latest version, when sending a chat message in the T3 Code desktop app, the status shows "working..." indefinitely. However, checking the underlying opencode CLI session directly shows the response has already been completed.

Steps to Reproduce

1. Install fresh T3 Code (Alpha) v0.0.23
2. Configure opencode as the provider (opencode CLI v1.14.48)
3. Send any chat message
4. Observe: T3 Code shows "working..." status indefinitely
5. Check opencode session via CLI — response is already complete

Expected Behavior

T3 Code should detect when the opencode CLI session has finished responding and update the UI accordingly (stop showing "working...").

Actual Behavior

"Working..." status persists forever, making the UI unusable.

Environment

• T3 Code version: 0.0.23 (Alpha)
• macOS (Apple Silicon)
• opencode CLI version: 1.14.48

Additional Context

Issue appeared after a recent update. The underlying agent (opencode) is functioning correctly — responses complete successfully via CLI. The problem is in T3 Code's detection/communication with the opencode CLI process — it doesn't seem to recognize when the session has finished.

Start by tracing the T3 Code desktop app's communication with the opencode CLI, focusing on how completion is detected and how the "working..." status is cleared. Reproduce with T3 Code 0.0.23 and opencode CLI 1.14.48; done means the UI stops showing "working..." after the CLI session has finished.