Feature/multiple direct likelihood

[adolgert]

1. Major Refactoring (15 files changed, +581/-290 lines):

• New file: src/sampler_builder.jl - Extracted sampler building logic from context.jl into a dedicated module
• Context interface overhaul (src/context.jl):
  • Context now stores and manages time internally
  • Changed enable! to accept relative times instead of absolute times
  • Simplified interface by removing explicit when parameters where context tracks time
  • Made SamplingContext mutable to track state

2. Multiple Direct Method Enhancements (src/sample/multiple_direct.jl):

• Added trajectory likelihood support to MultipleDirect sampler
• Added steploglikelihood() and trajectoryloglikelihood() functions
• Fixed method signature issues
• Made it a proper SSA{K,Time} subtype

3. Direct Method Updates (src/sample/direct.jl):

• Fixed trajectoryloglikelihood() to accept an end time parameter
• Improved likelihood calculation logic

4. Testing Infrastructure:

• New test file: test/erlang_loss.jl (183 lines) - Erlang loss system simulation for testing
• New test file: test/test_direct.jl (44 lines)
• New test file: test/test_sampler_builder.jl (45 lines)
• Updated existing tests to work with new context interface

5. Bug Fixes:

• Removed debug statements
• Fixed getindex function for prefix search
• Minor fixes to trajectory tracking

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 58.97436% with 48 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.97%. Comparing base (1906016) to head (15ac116).

Files with missing lines	Patch %	Lines
src/sample/multiple_direct.jl	26.08%	17 Missing ⚠️
src/context.jl	42.85%	12 Missing ⚠️
src/sampler_builder.jl	81.25%	12 Missing ⚠️
src/sample/direct.jl	0.00%	7 Missing ⚠️
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Additional details and impacted files

@@                  Coverage Diff                   @@
##           dev/sample-context      #94      +/-   ##
======================================================
- Coverage               72.05%   70.97%   -1.09%     
======================================================
  Files                      21       22       +1     
  Lines                    1045     1075      +30     
======================================================
+ Hits                      753      763      +10     
- Misses                    292      312      +20     

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