Add Buildkite workflow based on QuantumClifford structure

[Krastanov-agent]

Summary

• Adds comprehensive Buildkite workflow based on QuantumClifford.jl's well-organized structure
• Replaces existing GitHub Actions breakage workflow with Buildkite trigger
• Implements both base tests and JET static analysis in Buildkite
• Includes downstream dependency testing for quantum ecosystem packages

Changes Made

• New .buildkite/pipeline.yml:
  • Base package tests with Julia 1.x
  • JET static analysis tests using matrix configuration
  • Downstream testing for QuantumOpticsBase, QuantumOptics, QuantumSymbolics, QuantumClifford, and QuantumSavory
• Updated .github/workflows/breakage.yml: Simplified to trigger Buildkite pipeline via API

Benefits

• Leverages proven Buildkite infrastructure used by QuantumClifford
• Better resource management and parallelization for downstream tests
• Consistent testing approach across QuantumSavory ecosystem
• JET static analysis for improved code quality

Test plan

• Verify Buildkite pipeline configuration is valid
• Test downstream dependency builds complete successfully
• Confirm JET tests run and detect static analysis issues
• Ensure breakage workflow triggers Buildkite correctly

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 33.18%. Comparing base (13933af) to head (cf57137).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #69      +/-   ##
==========================================
+ Coverage   32.95%   33.18%   +0.22%     
==========================================
  Files          15       15              
  Lines         443      443              
==========================================
+ Hits          146      147       +1     
+ Misses        297      296       -1     

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