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.