fix: validate explicit algorithm order

[ShiroKSH]

Description

Fix explicit algorithm-order validation so that only a dependency placed in reverse order is rejected. Independent algorithms no longer make a valid custom order fail.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change which fixes an issue)

Testing

• Added a regression test covering both independent algorithms and a reversed dependency.
• Ran Python compilation for the changed source and test files.
• Ran a targeted behavioural smoke test against the changed validation function.

Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my code, especially for agent-assisted changes.

AI-assisted

This is an AI-assisted contribution. The change was independently reviewed against the order-graph semantics and covered with a focused regression test.