fix: support current opencode dev checkouts

[kitlangton]

What

Make opencode-drive start --dev work with current OpenCode V2 development checkouts and fail clearly for unsupported checkouts.

Before / After

Before: Drive always launched scripted servers with serve --service. Current V2 uses serve --register, so the server exited before its simulation backend became ready. Older checkouts without packages/simulation instead timed out waiting for endpoints they could never expose.

After: Drive selects the serve registration flag from the checkout shape and rejects checkouts without simulation support during preparation with an actionable error.

How

• packages/drive/src/instance/dev.ts validates packages/simulation and records the checkout's service flag.
• packages/drive/src/instance/runtime.ts uses that flag when launching the scripted server.
• packages/drive/test/instance/dev.test.ts covers legacy standalone V2, current V2, and unsupported checkouts.

Testing

• bun run check
• bun run test (265 tests passed)
• End-to-end smoke run against the current OpenCode V2 checkout: launched server and TUI, submitted a prompt, received a simulated response, captured a screenshot, and exited cleanly