Refactor AddTypeAnnotations for doc comment parsing

[trippwill]

With this change, doc comments will only be parsed for types that are in the same assembly as the root type.

Closes #69

[Copilot]

Copilot reviewed 5 out of 7 changed files in this pull request and generated no comments.

Files not reviewed (2)

• SharpSchema.sln: Language not supported
• src/SharpSchema/TypeHandlers/FallbackTypeHandler.cs: Evaluated as low risk

Comments suppressed due to low confidence (1)

src/SharpSchema/ConverterContext.cs:62

• The comment above the 'Defs' property should be updated to reflect its internal access level.

internal SortedDictionary<string, JsonSchemaBuilder> Defs { get; init; } = [];

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.47%. Comparing base (5208a76) to head (cf54745).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...rc/SharpSchema/TypeHandlers/FallbackTypeHandler.cs	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #79      +/-   ##
==========================================
+ Coverage   77.26%   77.47%   +0.20%     
==========================================
  Files          30       30              
  Lines         695      697       +2     
  Branches      118      118              
==========================================
+ Hits          537      540       +3     
+ Misses        128      127       -1     
  Partials       30       30              

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