Merge Gateway provider fails to initialize when the runtime npm install fails

Description

Merge Gateway is a registry provider whose npm package (merge-gateway-ai-sdk-provider) is not in BUNDLED_PROVIDERS, so opencode installs it from npm at runtime on first message. On machines where that install fails (proxy, registry config, offline cache), every message errors with Failed to initialize provider: merge-gateway, while bundled providers like @ai-sdk/anthropic keep working. Regenerating API keys, reconnecting, or restarting doesn't help since none of that touches the npm step. Reported by a Merge Gateway user via support (I work at Merge).

Plugins

None

OpenCode version

Reproduced on current dev from source

Steps to reproduce

1. rm -rf ~/.cache/opencode/packages
2. Make the npm registry unreachable, e.g. export npm_config_registry=http://127.0.0.1:9
3. Send any message with a merge-gateway/* model
4. Failed to initialize provider: merge-gateway on every message; anthropic/openai providers still work

Fix proposed in #46484: bundle the provider like venice/gitlab/openrouter.