.feature editing without glue

### 🤔 What's the problem you're trying to solve?

We entirely use Gherkin in early stages of design to agree on features and properly define them. The yellow underlines under every step are quite grating, and gives a bad impression to non-technical stakeholders when projected for the whole room to see.

### ✨ What's your proposed solution?

A `.vscode/settings.json` setting to make glue opt in.

### ⛏ Have you considered any alternatives or workarounds?

_No response_

### 📚 Any additional context?

_No response_

Start with the extension's settings handling and the proposed .vscode/settings.json entry, then trace how glue-related step diagnostics are enabled. Done means Gherkin files no longer show yellow underlines by default, while the new setting can opt glue checking back in.

Written by the indexing model from the issue text.