Fixed the choice of PULP solver issue

[lizliz]

Description

This change makes the PuLP solver selection explicit and environment-aware instead of relying on a bundled CBC binary from the local virtual environment.

The root cause was that the project could silently launch an incompatible CBC executable in the .venv, which caused Bad CPU type in executable failures on macOS when running the interleaving optimization. The fix prefers the active environment’s installed CBC binary, honors explicit solver path overrides, and uses the supported PuLP COIN_CMD(..., path=...) API for custom CBC locations.

This keeps solver selection controllable across environments and avoids other users hitting the same branch-specific architecture mismatch.

Motivation and Context

The interleaving optimization path calls into PuLP to solve the ILP. In this environment, the bundled CBC in the virtualenv was not compatible with the machine architecture, so optimization crashed before the actual algorithm could run.

This change is required to make the solver choice deterministic and safe across local developer environments, conda environments, and CI setups.

How has this been tested?

By running make tests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have incremented the version number in the pyproject.toml file if a new version needs to be pushed to pypi. Note that if the number isn't incremented, the package will not be pushed to pypi, which is useful if this PR is only for updating documentation.
• My code follows the code style of this project and I have run make format to clean up the code with black.
• My change requires a change to the documentation. I have updated the documentation as necessary and compiled locally to ensure it is clean.
• I have added tests to cover my changes, and all new and existing tests passed (run make tests).

[Copilot]

Copilot review overview

🟡 Changes recommended

Solver discovery does not match PuLP’s canonical names, and focused selector tests are missing.

Get a fresh assessment by requesting another Copilot review.

Review effort: Lite
Findings: 1 · 1

Open (2)

• Match PuLP canonical solver names to solver classes · New
• Add focused tests for solver selection behavior · New

What changed in this PR

This PR makes PuLP solver selection environment-aware and updates the package version.

Changes:

• Adds configurable solver and CBC path selection.
• Applies the selected solver to both ILP paths.
• Bumps the version to 0.1.17.

File	Summary
pyproject.toml	Updates the package version.
cereeberus/​cereeberus/​distance/​ilp.py	Adds solver selection and integrates it into ILP solving.

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