fix(opencode): connect disabled MCP after auth

[ClearWei]

Fixes #33915

Summary:

• Connect after OAuth with enabled forced on for the current run.
• Cover disabled OAuth MCP configs in the auth regression test.

Test:

• npx --yes bun@1.3.14 test test/mcp/oauth-auto-connect.test.ts --timeout 30000
• npx --yes bun@1.3.14 run typecheck
• npx --yes bun@1.3.14 x prettier --check packages/opencode/src/mcp/index.ts packages/opencode/test/mcp/oauth-auto-connect.test.ts

[github-actions]

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential duplicate found:

• PR fix(mcp): reconnect after OAuth even when server is disabled #33920: fix(mcp): reconnect after OAuth even when server is disabled
  • fix(mcp): reconnect after OAuth even when server is disabled #33920
  • This appears to be directly related—it addresses the same issue of reconnecting MCP after OAuth when the server/config is disabled, which is the core problem that PR fix(opencode): connect disabled MCP after auth #34189 fixes.

[github-actions]

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