attach client should not refresh models.dev on every connection #10781

Problem

When using opencode attach to connect to an already running opencode serve server, the client still performs a models.dev refresh on every connection, causing ~1 second delay.

Expected Behavior

The attach client should:

1. Skip models.dev network request
2. Reuse model information from the server
3. Connect instantly (< 100ms)

Current Behavior

$ time opencode attach http://localhost:4096 --version
INFO  2026-01-27T06:27:37 +20ms service=models.dev file={} refreshing
1.1.36
real    1.236s

The models.dev refreshing log appears even though the server already has this information cached.

Environment

• opencode version: 1.1.36
• macOS (Apple Silicon)
• Server running: opencode serve --port 4096
• Client: opencode attach http://localhost:4096

Impact

Every new terminal session has ~1 second startup delay, which defeats the purpose of the server/client architecture (fast reconnection).

Suggested Fix

• Move models.dev refresh to server-side only
• Client should fetch model list from server via the existing connection
• Or add --skip-model-refresh flag / OPENCODE_SKIP_MODEL_REFRESH env var