Add SliceSampling.jl adapter

[BJMCox]

Adds optional SliceSampling.jl support for transformed BAT targets.

• Uses BAT initialization, transforms, context RNG, and evaluated measures
• Preserves upstream log densities and transition diagnostics
• Reports autocorrelation effective sample size
• Tests a conjugate posterior, shaped values, sampler choice, and seeded replay

This targets many-changes because it uses the evaluation API from #564.

Tests:

• Optional suite: 11/11
• Full BAT suite: 22,564/22,564

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 65.47%. Comparing base (6e8795f) to head (08aee20).

Files with missing lines	Patch %	Lines
ext/BATSliceSamplingExt.jl	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #570      +/-   ##
==========================================
+ Coverage   65.45%   65.47%   +0.01%     
==========================================
  Files         121      122       +1     
  Lines        7060     7087      +27     
==========================================
+ Hits         4621     4640      +19     
- Misses       2439     2447       +8     

☔ 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.