Allow concurrent DBX Web query execution

[lipaopao000]

Summary

This change lets the Node Web backend execute SQL queries through /api/query/execute without first calling /api/connection/connect.

Why

When DBX_WEB_URL is set, both the CLI and MCP server use @dbx-app/node-core's Web backend. The current executeQuery() path calls /api/connection/connect before every /api/query/execute.

That pre-connect step makes concurrent CLI/MCP queries unreliable. Multiple simultaneous requests for the same connection can supersede one another during the connection attempt phase and fail with:

Connection attempt was superseded by a newer attempt

The Web query endpoint already accepts connectionId and creates or reuses a pool through the query execution path, so SQL queries do not need this UI-style connect step first.

Change

• Removed the pre-query ensureConnected(config) call from packages/node-core/src/web-backend.ts.
• Added a Web backend regression test that runs concurrent SQL queries and asserts that /api/connection/connect is not called.

Validation

pnpm --filter @dbx-app/node-core test
pnpm --filter @dbx-app/node-core build
pnpm --filter @dbx-app/cli test
pnpm --filter @dbx-app/mcp-server test

Observed locally:

• node-core: 18 test files passed, 86 tests passed
• CLI: 3 test files passed, 42 tests passed
• MCP server: 3 test files passed, 36 tests passed

Reproduction Context

With DBX_WEB_URL pointing at DBX Web, direct /api/query/execute calls can run concurrent Oracle queries successfully, but concurrent CLI/MCP queries fail before execution because they each call /api/connection/connect first.