Unpin highs

[tsmbland]

Description

Given that the optimisation problem is now sufficiently constrained (#1477 and #1478), we shouldn't get different results on different operating systems, or when updating highs. This PR confirms the latter point (well, at least moving from 2.3.0 to 2.4.0 - I can't guarantee that this will never be a problem). Given this, there's shouldn't be any need to pin highs any more

Fixes #1431

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc
• Update release notes for the latest release if this PR adds a new feature or fixes a bug
  present in the previous release

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.93%. Comparing base (c101c81) to head (58e1ad6).
⚠️ Report is 2 commits behind head on asset_equalisation.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           asset_equalisation    #1471   +/-   ##
===================================================
  Coverage               89.93%   89.93%           
===================================================
  Files                      60       60           
  Lines                    8595     8595           
  Branches                 8595     8595           
===================================================
  Hits                     7730     7730           
  Misses                    545      545           
  Partials                  320      320           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

Pull request overview

This PR removes the explicit pinning of the HiGHS solver crate versions now that the optimisation problem is sufficiently constrained to avoid platform-dependent results, addressing issue #1431.

Changes:

• Update highs from an exact pin (=2.3.0) to an unpinned compatible requirement (2.4.0) and remove the direct highs-sys dependency.
• Refresh Cargo.lock to the newer highs-sys (and related transitive) versions.
• Re-enable Dependabot updates for highs/highs-sys by removing the ignore entries.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Cargo.toml	Unpins HiGHS by moving from exact versions to a normal semver requirement and removing the direct highs-sys entry.
Cargo.lock	Updates the resolved dependency graph to highs 2.4.0 / highs-sys 1.15.0 and associated transitive crates.
.github/dependabot.yml	Stops ignoring HiGHS-related crates so Dependabot can propose future updates.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.