Code quality improvements — Aqua tests, Database import fix, remove Embedding wrapper

[ParamThakkar123]

Summary

19. Add Aqua.jl tests

Created test/aqua.jl with Aqua.test_all covering ambiguities, stale deps, deps compat, and piracy. Added Aqua to [extras] in Project.toml.

20. Manifest.toml

Verified: already untracked — .gitignore correctly excludes Manifest*.toml and no Manifest.toml exists in the git index.

21. Fix Database.jl fragile import

Replaced using ..Pgvector: convert + import Base: convert (which caused method ambiguity with Base) with a local _vector_to_pgarray helper. Removed the now-unused pgvector.jl submodule entirely.

22. Remove thin Embedding.jl wrapper

embedding.jl was a 3-line module that just delegated to RAGTools.build_index. Inlined build_index_rag into Utils and deleted the file.

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 27.27%. Comparing base (ab3aa76) to head (8c40129).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/database.jl	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
+ Coverage   22.98%   27.27%   +4.28%     
==========================================
  Files           6        4       -2     
  Lines          87       88       +1     
==========================================
+ Hits           20       24       +4     
+ Misses         67       64       -3     

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