Sidebar styling: long titles overflow in smart-contracts section

## Description

The sidebar in the new smart-contracts documentation section has styling issues where some entries overflow or display incorrectly. This was flagged during the review of #147.

**Screenshot from PR #147 review:**

## Details

The smart-contracts section has several nested categories (Accounts, Notes, Transactions) and pages with longer titles ("Cross-Component Calls", "Toolchain & Project Structure", "Patterns & Security") that cause the sidebar to overflow with broken formatting, particularly with code-highlighted text spilling outside the sidebar container.

## Context

Originally flagged in [PR #147 review](https://github.com/0xMiden/miden-docs/pull/147#discussion_r2802698201). Tracked as a separate issue since it is not blocking for that PR.

The issue is in the sidebar styling for the smart-contracts documentation section. Look at the CSS for the sidebar component, likely in a file like `sidebar.css` or within a React component. The screenshot shows overflow with long titles and code-highlighted text. Test by adjusting CSS properties like `overflow`, `text-overflow`, and `white-space` to ensure titles wrap or truncate properly within the container.

Rédigé par le modèle d'indexation à partir du texte de l'issue.