[CHORE]: Use idiomatic inherit syntax in Nix files

[anntnzrb]

Description

The Nix files in the repository use explicit assignment syntax instead of the more idiomatic inherit syntax.

Running statix check reports 10 W03/W04 warnings:

• W03: Assignment instead of inherit
• W04: Assignment instead of inherit from

Proposed Solution

Use idiomatic inherit syntax. This is a style-only change with no functional impact.

[anntnzrb]

PR: #6457