fix: expose AZP variants in region API

[samay2504]

This PR exposes the existing AZP variant solvers in the public region API so users can import AZPSimulatedAnnealing, AZPBasicTabu, and AZPReactiveTabu directly from spopt.region, and it adds a focused regression test to lock that import behaviour in place; the change is intentionally minimal and only surfaces already implemented classes without altering solver logic.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.9%. Comparing base (9b36063) to head (4744d69).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #514   +/-   ##
=====================================
  Coverage   76.9%   76.9%           
=====================================
  Files         29      29           
  Lines       3700    3700           
=====================================
  Hits        2846    2846           
  Misses       854     854           

Files with missing lines	Coverage Δ
spopt/region/__init__.py	100.0% <100.0%> (ø)

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[Copilot]

Pull request overview

This PR aims to make existing AZP “variant” implementations importable from the public spopt.region API (e.g., from spopt.region import AZPBasicTabu) and adds a small regression test to lock in that import behavior.

Changes:

• Re-export AZPBasicTabu, AZPReactiveTabu, and AZPSimulatedAnnealing from spopt.region.__init__.
• Update AZP tests to import the new public symbols.
• Add a regression test asserting the symbols are exposed.

Reviewed changes

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

File	Description
spopt/region/__init__.py	Re-exports AZP variant symbols from the package-level public API.
spopt/tests/test_region/test_azp.py	Adds/updates tests to validate (at least nominally) that the new imports work.

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