Add direct unit tests for solverforge-cvrp

[blackopsrepl]

Summary

solverforge-cvrp appears to expose meaningful routing and time-feasibility helpers without visible crate-local tests.

Problem

The crate contains nontrivial helper logic but does not appear to have direct deterministic unit coverage.

Why This Matters

This is public helper logic used in routing scenarios, and regressions should be caught inside the crate rather than only indirectly.

Proposed Work

• Add unit tests for distance helpers.
• Add unit tests for route assignment helpers.
• Add unit tests for time-window feasibility.
• Add edge-case coverage for empty fleets, invalid route positions, and boundary conditions.

Acceptance Criteria

• solverforge-cvrp has direct tests in the crate.
• Core helper behavior is covered by deterministic unit tests.

Source

Derived from PR #3 (PRODUCTION_REVIEW_ISSUES_2026-03-20.md).

[blackopsrepl]

Resolved by #20.

We added direct crate-local coverage for CVRP helper behavior, including distance meters, depot/load/capacity helpers, route-assignment helpers, and time-window feasibility checks.